Answer: - 894.6 kJ/mol.
Explanation:
Hess law is states that the changes in enthalpies in a chemical reactions is independent of the pathway between the initial and final states.
∆H is the change in the sum of the internal energy of a system.
We are to find the Value of ΔH°(rxn) for the equation:
NH3 (g) + 2 O2 (g) ⟶ HNO3 (g) + H2O (g). ----------------------------------(**).
From the series of equations given;
==> 4NH3 (g) + 5O2 (g) -------->4 NO(g) + 6H2O (l). ∆H = -1166.0 kJ/mol.--------------------------------------(1).
===> 2NO(g) + O2 (g) ------> 2NO2 (g). ∆H = -116.2 kJ/mol.---------------(2).
===> 3NO2 (g) + H2O (l) ---------> 2HNO3 (aq) + NO (g). ∆H = -137.3 kJ/mol.-------------------------------------(3).
The first thing to do is to multiply equation (2) by 3. Also, multiply equation (3) by 2. This will give us equation (4) and (5) respectively.
6NO + 3 O2 ----------------> 6NO2. ∆H= 3 × (-116.2 kJ/mol) = -348.6 kJ/mol. ------------------------------------(4).
6NO2 + 2 H2O ----------------> 4HNO3 + 2 NO. ∆H= 2 × (-137.3kj/mol) = -274.6 kJ/mol ---------------------------(5).
Next, add equations (4) and (5) to give;
4NO +3O2 +2H2O -------------> 4HNO3. ∆H = -623.2 kJ/mol. -----(6).
Add this equation to the equation (1) from above, we have;
4NH3 + 8O2 --------------> 4HNO3 + 4H2O. ∆H= -1789.2 kJ/mol. --------(7).
Then, divide the equation (7) above by 2 to give us back the equation (**).
NH3 (g) + 2 O2 (g) ⟶ HNO3 (g) + H2O (g). ∆H= -894.6 kJ/mol.
Δ H^∘ (rxn)= - 894.6 kJ/mol.
Identify the numbers from the statements above as exact or measured. Sort these numbers into the proper categories.
Answer:
Here is a similar question ; Identify the numbers from the statements above as exact or measured Sort these numbers into the proper categories. 93 g of silver, One minute, 2.20 lb ,One kilogram ,27 miles ,One yard, 100 g of sterling silver ,60 s, 1gal ,3 ft Exact Measured
Explanation:
Here is a similar question ; Identify the numbers from the statements above as exact or measured Sort these numbers into the proper categories. 93 g of silver, One minute, 2.20 lb ,One kilogram ,27 miles ,One yard, 100 g of sterling silver ,60 s, 1gal ,3 ft Exact Measured
Exact number are known from scientific research that has been proven to be true and widely acceptable or are known from true definition. for example 0 degree celsius = 273k, 1atm = 101.325 kPa
while measured numbers are not widely acceptable, they are as a result of individual measurement and discretion. A may measure the mass of a stone to be 3.5g, another person B may measure the same stone and arrive at 3.4g.
exact numbers ; one minutes, One yard, One kilogram, 1gal, 3ft, 100g of sterling silvermeasured numbers ; 93g of silver, 2.20 lb, 27 milesFunctional groups create active sites in molecules. The polar part of a molecule that can hydrogen bond to water is said be hydrophilic. Pi (π) bonds create active sites and will react with electron-deficient species. A electronegative heteroatom like nitrogen, oxygen, or a halogen makes a carbon atom ____________ . The nonpolar part of a molecule that is not attracted to water is said to be hydrophobic.
Answer:
Polar/Hydrophilic
Explanation:
Fluorine, Nitrogen and Oxygen are strong electronegative atoms and by definition, Electronegativity is the amount of pull or the high affinity of an atom to electrons.
Polar bond occurs when there is a high difference between the electronegativity value of both atoms that take part in the bond.
A polar molecule has a net dipole from the distribution of its positive and negayive charges. Hydrophobic and Hydrophilic (in chemistry, Polar) are terms dependent on the overall distribution of charge in its molecule.
Therefore, bonds between C-N, C-O and C-Cl are polar covalent bonds a d this is because of the jigh electronegativity possessed by Nitrogen, Oxygen and Chlorine.
How many hydrogen atoms are in 35.0 grams of hydrogen gas? How many hydrogen atoms are in 35.0 grams of hydrogen gas? 4.25 × 1025 2.12 × 1025 1.05 × 1025 2.09 × 1025 none of the above
Answer:
1.05 × 10²⁵ atoms H₂
General Formulas and Concepts:
Atomic Structure
Reading a Periodic TableMolesStoichiometry
Using Dimensional AnalysisExplanation:
Step 1: Define
[Given] 35.0 g H₂
[Solve] atoms H₂
Step 2: Identify Conversions
Avogadro's Number - 6.022 × 10²³ atoms, molecules, formula units, etc.
[PT] Molar Mass of H - 1.01 g/mol
Molar Mass of H₂: 2(1.01) = 2.02 g/mol
Step 3: Convert
[DA] Set up: [tex]\displaystyle 35.0 \ g \ H_2(\frac{1 \ mol \ H_2}{2.02 \ g \ H_2})(\frac{6.022 \cdot 10^{23} \ atoms \ H_2}{1 \ mol \ H_2})[/tex]Simplify [Cancel out units]: [tex]\displaystyle 1.04342 \cdot 10^{25} \ atoms \ H_2[/tex]Step 4: Check
Follow sig fig rules and round. We are given 3 sig figs.
1.04342 × 10²⁵ atoms H₂ ≈ 1.04 × 10²⁵ atoms H₂
Topic: AP Chemistry
Unit: Atomic Structure
Final answer:
To find the number of hydrogen atoms in 35.0 grams of hydrogen gas, we calculated the moles of hydrogen gas and used Avogadro's number. We determined that there are 2.09 × 1025 hydrogen atoms in 35.0 grams of hydrogen gas.
Explanation:
To determine how many hydrogen atoms are in 35.0 grams of hydrogen gas, we use Avogadro's number and the concept of molar mass. The molar mass of hydrogen gas (H2) is 2.0158 grams per mole. First, we calculate the number of moles in 35.0 grams of hydrogen gas:
(35.0 grams H2) ÷ (2.0158 grams/mol) = 17.37 moles H2
Since each mole of hydrogen gas contains two hydrogen atoms, we need to multiply the number of moles by Avogadro's number, which is 6.022 × 1023 atoms/mol:
(17.37 moles H2) × (6.022 × 1023 molecules H2/mol) × (2 atoms H/molecule H2)
After calculating, we find that there are 2.09 × 1025 hydrogen atoms in 35.0 grams of hydrogen gas. Therefore, the correct answer is 2.09 × 1025.
A neutral atom and an ion of the same element have the same number of _______. They have a different number of _______ and hence reactivity.
Answer:
a. Protons
b. Electrons
Explanation:
The atomic number of an element is also the proton number. Since the atom is neutral, the proton number and the electron number are equal. But this is different for an ion in that the element has either gain or loss an electron and so, the electron number differ from the proton number.
Consider the five balanced chemical reactions listed below, all using O2 as a reactant. Normally, O2 is an excess reagent for reactions because there is a large amount of it available in the air. For this question, suppose that you have5.73 moles of O2 and1.70 moles of any of the other reactants in every equation. Select those equations below in which O2 would be the limiting reactant.
A.C6H12O6(s) + 6 O2(g) → 6 CO2(g) + 6 H2O(g)B.C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g)C.H2S(g) + 2 O2(g) → SO3(g) + H2O(g)D.4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g)E.None because in all the reactions O2 is in excess
Answer: option E. None because in all the reactions O2 is in excess
Explanation:
In the above reactions, only Reaction A and Reaction B have oxygen (O2) as the limiting reactant. For the rest of the reactions, the other compound will be used up before all the O2 is spent.
Explanation:In every reaction, you have 5.73 moles of O2 and 1.70 moles of the other reactants. You can determine which of the two reactants are limiting (which will be consumed first) by comparing the number of moles of that reactant divided by its stoichiometric coefficient (the numbers in front of the chemicals in the reaction) to the same calculation for the other reactant.
For reaction A, C6H12O6(s) + 6 O2(g) → 6 CO2(g) + 6 H2O(g), the ratios are 5.73 moles O2/6 and 1.70 moles C6H12O6/1. So O2 is limiting. For reaction B, C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g), the ratios are 5.73 moles O2/5 and 1.70 moles C3H8/1. So O2 is limiting. For reaction C, H2S(g) + 2 O2(g) → SO3(g) + H2O(g), the ratios are 5.73 moles O2/2 and 1.70 moles H2S/1. In this case, H2S is limiting, not O2. For reaction D, 4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g), the ratios are 5.73 moles O2/5 and 1.70 moles NH3/4. In this case, NH3 is limiting, not O2. Learn more about Limiting Reactant here:
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Gas is $2.50/gal at Station A and 85 cents/L at Station B. A) Convert the cost of gas at Station B to $/gal. B) At which station would you buy gas?
Answer:
85 cents/L is equal to 3.2176$/gallon.
gas wiuld be heaper to buy from the station A.
Explanation:
As 85 cents/L is more than $2.5/gallon therefore buying gas from station A would be cheaper than the other one.
A chemist adds .25L of a .11M potassium dichromate solution to a reaction flask. Calculate the mass in grams of potassium dichromate the chemist has added to the flask. Round your answer to significant digits.
Answer: 8.2 grams of potassium dichromate the chemist has been added to the flask.
Explanation:
Molarity is defined as the number of moles of solute dissolved per liter of the solution.
To calculate the number of moles for given molarity, we use the equation:
[tex]\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}[/tex] .....(1)
Molarity of potassium dichromate solution = 0.11 M
Volume of solution = 0.25 L
Putting values in equation 1, we get:
[tex]0.11M=\frac{\text{Moles of potassium dichromate}}{0.25L}\\\\{\text{Moles of potassium dichromate}}={0.11mol/L\times 0.25L}=0.028mol[/tex]
Mass of potassium dichromate =[tex]moles\times {\text {molar mass}}=0.028mol\times 294g/mol=8.2g[/tex]
Thus mass in grams of potassium dichromate the chemist has added to the flask is 8.2.
To calculate the mass of potassium dichromate, use the equation moles = volume (L) × concentration (mol/L), and then multiply the moles by the molar mass of K₂Cr2O7. Round your answer to the correct number of significant digits.
Explanation:To calculate the mass of potassium dichromate that the chemist added to the flask, we can use the equation:
moles = volume (L) × concentration (mol/L)
First, convert the volume to liters by dividing it by 1000. Then, use the equation with the given volume and concentration to find the moles of potassium dichromate. Finally, multiply the moles by the molar mass of potassium dichromate to get the mass in grams. The molar mass of K₂Cr2O7 is 294.185 g/mol.
mass = moles × molar mass
Make sure to round your answer to the correct number of significant digits based on the given information.
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Azobisisobutyronitrile (AIBN) is commonly used as a radical initiator. Use correct arrow formalism to show this process.
Answer: AIBN is good radical initiator
Explanation:
A radical in organic chemistry refers to any specie having a single unshared electron. An initiator is any specie capable of producing radicals thus starting up a chain reaction. Azobisisobutyronitrile is a good initiator basically owing to its structure. It forms radicals by breaking up to release nitrogen gas as shown in the image attached. The two radicals formed both contain the -CN group which stabilizes the radical.
The solid XY decomposes into gaseous X and Y: XY(s) m X(g) + Y(g) Kp = 4.1 (at 0 °C) If the reaction is carried out in a 22.4 L container, which initial amounts of X and Y will result in the formation of solid XY?a) 5 mol X; 0.5 mol Yb) 2.0 mol X; 2.0 mol Yc) 1 mol X; 1 mol Yd) none of the above
Answer:
None of the conditions will favor either the forward reaction or backward reaction , hence the answer is D
Explanation:
The principle of chemical Equilibrium is applied here, where the concentration of the reactants or the forward reaction is same as the concentration of the products or the backward reaction. The equilibrium constants is also involved here, K can be in terms of pressure (Kp) or concentration (Kc) hence equilibrium constant is the ration of the concentration of the products to the concentration of the reactants raised to the power of the coefficient of the reactants and products.Partial pressure , total pressure and the mole fraction relationship is also appliedThe step by step explanation is as shown in the attachment below.It's challenging to determine the precise initial amounts of gaseous elements X and Y in the reaction, XY(s) → X(g) + Y(g), with the given Kp and the conditions provided. Based on the data provided, the accurate answer would be 'none of the above'.
Explanation:This question involves equilibrium in chemical reactions, specifically the concept of Kp, the equilibrium constant under constant pressure circumstances. In its simplest form, it represents a ratio of the concentrations of products and reactants, each raised to the power of their respective stoichiometric coefficients in the balanced chemical equation. In this context, if the reaction XY(s) → X(g) + Y(g) has a Kp = 4.1, it means that when equilibrium is reached, the ratio [X][Y]/[XY] is 4.1.
Given that one mole of gas at 0°C and 1 atmosphere of pressure occupies a volume of 22.4L (standard molar volume), we can establish the initial conditions of X and Y using the stoichiometric ratio. However, without additional specifics on the initial conditions of the solid XY such as its volume or weight, it's challenging to determine precise initial amounts of X and Y. Therefore, the accurate answer from the given choice would be (d) none of the above.
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What is the final pH of a solution when 0.1 moles of acetic acid is added to water to a final volume of 1L?
Answer:
The pH of solution is 2.88 .
Explanation:
The reaction is :
[tex]CH_3COOH-->CH_3COO^-+H^+[/tex]
We know, [tex]K_a[/tex] for this reaction is = [tex]1.76\times 10^{-5}.[/tex]
Also, since volume of water is 1 L.
Therefore, molarity of solution is equal to number of moles.
Also, [tex]K_a=\dfrac{[CH_3COO^-][H^+]}{[CH_3COOH]}[/tex]
Let, amount of [tex]CH_3COO^- and\ H^+[/tex] produce is x.
So,
[tex]K_a=\dfrac{[x][x]}{[0.1]}\\1.76\times 10^{-5}=\dfrac{[x][x]}{[0.1]}[/tex]
[tex]x=0.0013\ mol.[/tex]
We know, [tex]pH=-log{x}=-log(0.0013)=2.88[/tex]
Therefore, pH of solution is 2.88 .
Hence, this is the required solution.
Final answer:
The final pH of a 1L solution containing 0.1 moles of acetic acid is determined by using the hydrogen ion concentration resulting from its dissociation. The pH is calculated to be approximately 2.879 following the calculation procedures outlined for weak acids.
Explanation:
Calculating pH of an Acetic Acid Solution
The final pH of a solution can be determined by calculating the hydrogen ion concentration ([H+]) resulting from the dissociation of acetic acid in water. Given that we have 0.1 moles of acetic acid added to water to make 1L of solution, the molarity of acetic acid is 0.100 M. Acetic acid (CH₃COOH) is a weak acid, and its dissociation in water is represented by the following equation:
CH₃COOH <--> CH₃COO⁻ + H⁺
We use the acid dissociation constant (Ka) to solve for [H+]. For acetic acid, Ka = 1.8 x 10⁻⁵ M. The calculation involves setting up an ICE table and using the quadratic formula, as outlined in the subject's textbook or reference. The calculation typically results in a hydrogen ion concentration of 1.32 x 10⁻³ M.
The pH is found by taking the negative logarithm of the hydrogen ion concentration:
pH = -log(1.32 x 10⁻³) = 2.879
Therefore, the pH of a 0.100 M solution of acetic acid is approximately 2.879.
What is the pH of 100 mL of a 50 mM solution of benzoic acid is added to 70 mL of a 50 mM NaOH solution?
Answer: The pH of the solution is 4.57
Explanation:
To calculate the number of moles for given molarity, we use the equation:
[tex]\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution (in mL)}}[/tex]
For benzoic acid:Molarity of benzoic acid = 50 mM = 0.05 M (Conversion factor: 1 M = 1000 mM)
Volume of solution = 100 mL
Putting values in above equation, we get:
[tex]0.05M=\frac{\text{Moles of benzoic acid}\times 1000}{100mL}\\\\\text{Moles of benozic acid}=\frac{(0.05\times 100)}{1000}=0.005mol[/tex]
For sodium hydroxide:Molarity of sodium hydroxide = 50 mM = 0.05 M
Volume of solution = 70 mL
Putting values in above equation, we get:
[tex]0.05M=\frac{\text{Moles of sodium hydroxide}\times 1000}{50mL}\\\\\text{Moles of sodium hydroxide}=\frac{0.05\times 70}{1000}=0.0035mol[/tex]
The chemical reaction for sodium hydroxide and benzoic acid follows the equation:
[tex]C_6H_5COOH+NaOH\rightarrow C_6H_5COONa+H_2O[/tex]
Initial: 0.005 0.0035
Final: 0.0015 - 0.0035
Volume of solution = 100 + 70 = 170 mL = 0.170 L (Conversion factor: 1 L = 1000 mL)
To calculate the pH of acidic buffer, we use the equation given by Henderson Hasselbalch:
[tex]pH=pK_a+\log(\frac{[salt]}{[acid]})[/tex]
[tex]pH=pK_a+\log(\frac{[C_6H_5COONa]}{[C_6H_5COOH]})[/tex]
We are given:
[tex]pK_a[/tex] = negative logarithm of acid dissociation constant of benzoic acid = 4.2
[tex][C_6H_5COONa]=\frac{0.0035}{0.170}[/tex]
[tex][C_6H_5COOH]=\frac{0.0015}{0.170}[/tex]
pH = ?
Putting values in above equation, we get:
[tex]pH=4.2+\log(\frac{0.0035/0.170}{0.0015/0.170})\\\\pH=4.57[/tex]
Hence, the pH of the solution is 4.57
Why does ΔG for a reaction scale with reaction quantity but E does not? For example, ΔG0 rxn for the combustion of 1 mol of hydrogen is 1 × –237 kJ∕mol = –237 kJ, CHAPTER EXERCISES 73 while ΔG0 rxn for the combustion of 2 mol of hydrogen is 2 × –237 kJ∕mol = –474 kJ. In both
Answer:
This is as a result of their property type
ΔG is extensive and E is Intensive. The explanation is as given below
Explanation:
Basically both ΔG and the cell potential or the electromotive force (E.M.F) has some disparity especially in their spontaneity, for spontaneous reaction ΔG = -ve while E = +ve and vice versa. But the most important disparity is their state function i.e one is intensive and the other is extensive property.
ΔG is an example of an extensive property, they are properties whose value is dependent on the volume or the size of the system. other examples are mass, volume etc.
E on the other hand is an intensive property, they are properties whose value is not dependent on the size of the system. As such, this differences explains why ΔG for a reaction scale with a reaction quantity and E does not.
The change in Gibbs free energy (ΔG) for a reaction scales with reaction quantity because it is an extensive property, while the standard electrode potential (E) does not scale with reaction quantity because it is an intensive property.
Explanation:The change in Gibbs free energy (ΔG) for a reaction scales with reaction quantity because it is an extensive property, meaning it depends on the amount of substance involved in the reaction. On the other hand, the standard electrode potential (E) does not scale with reaction quantity because it is an intensive property, meaning it is independent of the amount of substance.
For example, in the combustion of hydrogen, the standard Gibbs free energy change (ΔG°) for the reaction is -237 kJ/mol for 1 mole of hydrogen and -474 kJ/mol for 2 moles of hydrogen. Since ΔG is an extensive property, it doubles when the quantity of hydrogen doubles. However, the standard electrode potential (E°) remains the same regardless of the quantity of hydrogen.
In summary, the scaling of ΔG with reaction quantity and the independence of E from reaction quantity are due to the differences in their nature as extensive and intensive properties, respectively.
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Salts are always ________. Select one: a. single covalent compounds b. hydrogen bonded c. ionic compounds d. double covalent compounds
Answer:
C
Explanation:
The chemical formula of salt is NaCl (sodium chloride).
Na is a metal and Cl is a non-metal.
This means that NaCl is an ionic compound.
Covalent compound is a compound made up of non-metal atoms only.
Salts are always ionic compounds. Therefore, option C is correct.
An ionic compound is a type of chemical compound that is composed of ions held together by electrostatic forces of attraction.
Ionic compounds play vital in various applications, such as in the formation of salts, the electrolysis of compounds, and the construction of solid-state electronic devices.
Salts are a specific type of ionic compound. They are compounds formed when an acid reacts with a base through a chemical reaction called neutralization.
Salts consist of cations (positively charged ions) and anions (negatively charged ions) held together by ionic bonds.
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A block of metal has a width of 3.2 cmcm, a length of 17.1 cmcm, and height of 5.0 cmcm . Its mass is 1.2 kgkg . Calculate the density of the metal. Express your answer to two significant figures and include the appropriate units.
Answer:
≅ 4.39 gm/cm^3
Explanation:
Given data:
width of block =3.2 cm
length = 17.1 cm
height = 5.0 cm
Mass = 1.2 kg
Therefore volume= width×length×height = 3.2×17.1×5= 273.6 cm^3
now, density = mass/volume
calculating density in gm/cm^3
= 1200/273.6 = 4.38596
≅ 4.39 gm/cm^3
Carbon dioxide and an unknown gas start to effuse from a container and the carbon dioxide takes 4.69 times as long to escape as the unknown gas. What is the identity of the unknown gas?
Answer: the gas is lighter than CO2 and it is hydrogen
Explanation:Please see attachment for explanation
Indicate whether each of the following statements is TRUE or FALSE 1. A sharp melting point for a crystalline organic material always indicates a pure single compound 2. A molecular size impurity always lowers the melting point of an organic compound 3. If the addition of a sample of compound A to compound B does not change the melting point of B, A and B must be identical 4. An eutectic mixture has a sharp melting point Answer 4 Melting and freezing points of a pure compound are identical
Answer:1. False, 2. False, 3. True, 4. True
Explanation:
1. FALSE. Pure crystalline solids have sharp melting points, while the present of impurity lower the melting point. This is True, but the exception is a eutectic mixture. A properly mixed eutectic mixture have a sharp melting point also.
2. FALSE, although the present of impurity lower the melting point of a organic compound, but if a molecular size impurity with a significantly higher melting point and is present in large quantities the melting point of the organic compound will not be lowered.
3. TRUE, two compounds with same melting point, when mixed together will not change the melting point of either compounds. But if A has higher MP than B and the addition of A to B creates mixture with same melting point as pure A then the statement will be false.
4. TRUE, a properly mixed eutectic mixture will have a sharp melting point.
Melting point and freezing point of a pure compound will be identical because the liquid form of a pure substance when cooled it forms a stable arrangement that supercooling is prevented, freezing occur at the same temperature at which the pure solid phase melts
Draw the structural formula for 1-octyne. Click the "draw structure" button to launch the drawing utility.
Answer:
Explanation:
1 - Octyne is a member of the Alkyne family. Alkyne has a general formular is CnH2n-2 which is a homologous series with a least one carbon - carbon triple bond.
Where n is the number of carbon atoms needed in the structure.
The "1" prefix is an indicator for where the triple bond of the compound will be found which is at carbon -1. Because of its triple bond it is termed an unsaturated hydrocarbon. Their properties include:
1. Highly reactivity
2. Hydrophobic compound.
Octa- decribes the number of carbon atoms present in the compound which is 8. Also note that, it is not a cycloalkyne but a straight chain compound with a triple bond at one end.
So using the general formular, CnH2n-2
For n = 8,
1-Octyne is C8H14
Below in the attac is the structural formula of 1 - Octyne
Answer:
Explanation:
1-Octyne is a member of the Alkyne series, Alkyne is a homologous series with the general molecular formula;
CnH2n-2
n is a positive whole number which equal to or greater than 2.
i.e n= number of carbon given
In the case of the compound given (1-Octyne), the prefix “Oct” means 8, which is the number of
carbon atoms present in the compond while the suffix “yne” is
coined from the family name “Alkyne”
Therefore, C8H(2x 8) – 2 = C8H16-2 = C8H14
It is an unsaturated hydrocarbon, each alkyne molecule contains four hydrogen atoms
corresponding to alkane and two hydrogen atom less than the corresponding alkene. This is because
each alkyne molecule contains a carbon-carbon triple bond, where two carbon atoms are bonded
to each other by the sharing of three pairs of electrons.
The Alkyne family show a higher degree of unsaturation than the alkenes, hence they are chemically
reactive than alkane and alkene .
Polonium-209, an alpha emitter, has a half-life of 102 years.How many alpha particles are emitted in 1.0 s from a 1.0 ngsample of 209Po?
The number of alpha particles emitted from a 1.0ng sample of Polonium-209 in 1.0s depends on the specifics of the isotope's half-life and the initial amount of the isotope. The emissions of these alpha particles are part of the isotope's decay process.
Explanation:The half-life concept is key in understanding the decay of radioactive isotopes like polonium-209. Given that polonium-209 is an alpha emitter, it releases alpha particles during its decay process. These alpha particles are essentially helium-4 nuclei (two protons and two neutrons).
Understanding the number of alpha particles emitted in a certain time requires the understanding of the isotope's half-life and atomic decay. However, without knowing the specific numbers of atoms present in the given 1.0 ng sample of 209Po, it is difficult to provide a precise number of alpha particles emitted in 1.0 s. You would need to make use of the radioactive decay formula N = N0e^-λt where N0 represents the initial amount of the isotope, N represents the remaining amount of the isotope, λ represents the decay constant, and t represents time.
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Write the electron arrangement for each of the following atoms:(Example sodium 18,1)a. phosphorusb. neonc. sulfurd. magnesiume. aluminumf. fluorine
Answer:
2 8 5
2 8
2 8, 6
2 8 2
2 8 3
2 7
Explanation:
This is your question :
Write the electron arrangement for each of the following atoms:(Example sodium is 2,8,1)
a. phosphorus
b. neon
c. sulfur
d. magnesium
e. aluminum
f. fluorine
Phosphorus is an element in period 3. phosphorus has an atomic number of 15 and it contains 15 electrons. The electron arrangement can be computed as follow ;
2 8 5
This means is has 2 electrons at the first energy level, 8 electron at the second energy level and 5 electron at the third energy level. Base on it configuration phosphorus requires 3 electrons to fulfill it octet rule .
Neon is grouped as a noble gas or inert gas because of it less reactive nature . The atomic number of Neon is 10. The electron arrangement can be computed as follows;
2 8
This means it has 2 electrons on the first energy level and 8 electrons on the second energy level. Neon is in period 2 on the periodic table. Neon electron configuration shows it has fulfilled it octet rule, this is why it rarely goes into a reaction with other elements.
Sulfur
Sulfur has an atomic number of 16 . The electronic configuration is as follows ;
2 8, 6
Sulfur is in period 3 base on it configuration . it possess three energy level with 2 electrons at the first energy level , 8 electrons at the second energy level and 6 at the third energy level.
Magnesium
Magnesium has an atomic number of 12 . Magnesium is in period 3 in the periodic table and are also known as the alkali earth metals. The electronic configuration is as follows ;
2 8 2
The three energy level has 2 electrons, 8 electrons and finally 2 electrons. Magnesium is reactive.
Aluminium
Aluminium has an atomic number of 13 . Aluminium is in period 3 . The electronic configuration is as follows;
2 8 3
The three energy level has 2 electrons, 8 electrons and 3 electrons each .
Florine
Florine has an atomic number of 9. Florine is in period 2 on the periodic table. The electronic configurations is as follows ;
2 7
The two energy level has 2 electrons and 6 electrons respectively .
Draw the sulfur‑containing product of the oxidation reaction between two 2‑methyl‑1‑propanethiol molecules. Include all hydrogen atoms.
Final answer:
The sulfur-containing product of the oxidation of two 2-methyl-1-propanethiol molecules is a disulfide, where the sulfur atoms form a bond between the two original thiol molecules, resulting in a dimer.
Explanation:
The student has asked for the sulfur-containing product of the oxidation reaction between two 2-methyl-1-propanethiol molecules. In the presence of mild oxidizing agents such as oxygen, sulfur atoms can be oxidized from the sulfhydryl (S-H) groups present in 2-methyl-1-propanethiol. When two such sulfur atoms, each with an unpaired electron, come into contact, they can form a sulfur-sulfur bond (disulfide bond), resulting in the dimerization of the two thiol molecules.
The chemical formula of 2-methyl-1-propanethiol is CH3CH2CH(SH)C(CH3)2. Upon oxidation, the sulfur atoms from two of these molecules will bond together to form a disulfide. The resulting molecule will be CH3CH2CH(S-S)CH2C(CH3)2.
For this question, the "entropy term" refers to "-TΔS". Addition reactions are generally favorable at low temperatures because ________.
Answer:
Lowering the temperature typically reduces the significance of the decrease in entropy. That makes the Gibbs Free energy of the reaction more negative. As a result, the reaction becomes more favorable overall.
Explanation:
In an addition reaction there's a decrease in the number of particles. Consider the hydrogenation of ethene as an example.
[tex]\rm H_2C\text{=}CH_2\; (g) + H_2\; (g) \stackrel{\text{Ni}^\ast}{\to} H_3C\text{-}CH_3\; (g)[/tex].
When [tex]\rm H_2[/tex] is added to [tex]\rm H_2C\text{=}CH_2[/tex] (ethene) under heat and with the presence of a catalyst, [tex]\rm H_3C\text{-}CH3[/tex] (ethane) would be produced.
Note that on the left-hand side of the equation, there are two gaseous molecules. However, on the right-hand side there's only one gaseous molecule. That's a significant decrease in entropy. In other words, [tex]\Delta S < 0[/tex].
The equation for the change in Gibbs Free Energy for a particular reaction is:
[tex]\Delta G = \Delta H + (\underbrace{- T \, \Delta S}_{\text{entropy}\atop \text{term}})[/tex].
For a particular reaction, the more negative [tex]\Delta G[/tex] is, the more spontaneous ("favorable") the reaction would be.
Since typically [tex]\Delta S < 0[/tex] for addition reactions, the "entropy term" of it would be positive. That's not very helpful if the reaction needs to be favorable.
[tex]T[/tex] (absolute temperature) is always nonnegative. However, lowering the temperature could help bring the value of
CFC-11 (trichlorofluoromethane, CCl3F) has been used for many years as the working fluid in refrigerators. Given its heat of vaporization is 26.88 kJ/mol and its entropy of vaporization is 90.51 J/(mol ⋅ K), what is the boiling point of CFC-11?
Answer:
297.0 K
Explanation:
Given data
Enthalpy of vaporization (ΔHvap): 26.88 kJ/mol = 26.88 × 10³ J/molEntropy of vaporization (ΔSvap): 90.51 J/(mol ⋅ K)Boiling point (Tb): ?We can find the boiling point of CFC-11 using the following expression.
ΔSvap = ΔHvap/Tb
Tb = ΔHvap/ΔSvap
Tb = (26.88 × 10³ J/mol)/(90.51 J/(mol ⋅ K))
Tb = 297.0 K
½ H₂(g) + ½ I₂(s) --> HI(g) ΔH= 26 kJ/mol
½ H₂(g) + ½ I₂(g) --> HI(g) ΔH= -5.0 kJ/mol
Based on the information above, what is the enthalpy change for the sublimation of iodine, represented by I₂(s) --> I₂(g)?
a) 15 kJ/mol
b) 21 kJ/mol
c) 31 kJ/mol
d) 42 kJ/mol
e) 62 kJ/mol
The enthalpy change for the sublimation of iodine, represented by I₂(s) → I₂(g), is 31 kJ/mol.
Explanation:The enthalpy change for the sublimation of iodine, represented by I₂(s) → I₂(g), can be determined by comparing the enthalpy changes of the two given reactions. Since the equation ½ H₂(g) + ½ I₂(g) → HI(g) has a lower enthalpy change (-5.0 kJ/mol) compared to the equation ½ H₂(g) + ½ I₂(s) → HI(g) (26 kJ/mol), it means that the phase change from solid iodine to gaseous iodine requires an additional amount of energy. Thus, the enthalpy change for the sublimation of iodine is the difference between the two reaction enthalpies, which is 31 kJ/mol.
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For the following formula, C7H10NBr, calculate the IHD and select all the types of unsaturation that might be present in the molecule based on the IHD.
The molecule C7H10NBr has an Index of Hydrogen Deficiency (IHD) of 4, indicating 4 degrees of unsaturation. These could be a combination of double bonds, triple bonds, or rings.
Explanation:The Index of Hydrogen Deficiency (IHD) or Degree of Unsaturation for a molecule can be calculated using the formula IHD = 1/2(2C + 2 + N - X - H), where C is the number of Carbons, N the number of Nitrogens, X the number of Halogens, and H the total Hydrogen count. For the molecule C7H10NBr, applying the formula would yield:
IHD = 1/2(2*7 + 2 + 1 - 1 - 10) = 4
This means there are 4 degrees of unsaturation present in the molecule. The types of unsaturation could be double bonds, triple bonds, or rings. In this case, with a value of 4, it could be 4 double bonds, or 2 double bonds and 2 rings, or 2 rings and 1 triple bond, or 1 ring and 3 double bonds, or 2 triple bonds, and many more combinations.
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The Index of Hydrogen Deficiency for the compound C₇H₁₀N Br is 4, which indicates that the molecule can have a combination of 4 double bonds or 4 rings or a mix of both.
Explanation:The Index of Hydrogen Deficiency (IHD) is a count of how many molecules of H2 are missing from an alkane having the same number of carbon atoms. It's used to identify the number of rings and/or double bonds in organic compounds. For the compoundC₇H₁₀N Br, consider that Br adds 1 to the hydrogen count, and N subtracts 1. Thus, the IHD calculation would be: IHD= (2*C + 2 + N - X - H)/2 = [2*7 + 2 +1 -0 -10]/2 = 4
Since it has an IHD of 4, it indicates that the molecule can have a combination of 4 double bonds or 4 rings or a mix of both.
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Choose the aqueous solution below with the highest freezing point. These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable. Choose the aqueous solution below with the highest freezing point. These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.
a. 0.200 m Ba(NO3)2
b. 0.200 m Mg(ClO4)2
c. 0.200 m HOCH2CH2OH
d. 0.200 m Na3PO3
Answer: c. 0.200 m HOCH2CH2OH
Explanation:
The collective properties of solvents expressed that the freezing point of water is lowered when solute particles are dissolved in it.
When more particles are dissolved, the more the freezing point is deepened and lowered.
Here, all the molarities are equal, the deciding factor in measuring the lowering will be which substance produces the fewest particles in solution; then we relate it to lowering of the freezing point.
Ba(NO3)2 ---> Ba2+ + 2NO3(1-)
1 mol releases 3 mol of ions.
Mg(ClO4)2 ---> Mg2+ + 2ClO4(1-)
1 mol releases 3 mol of ions.
HOCH2CH2OH is covalent and doesn't ionize.
1 mol in water is just 1 mol of molecules.
Na3PO3 ---> 3Na+ + PO3(1-)
1 mol releases 4 mol ions.
The substance that produces the fewest particles in solution is the 0.200 m HOCH2CH2OH
The solution with the highest freezing point will be the one that forms the fewest particles when dissolved. In this case, that would be the ethylene glycol solution (HOCH2CH2OH), because it does not ionize in solution and therefore has a van't Hoff factor of 1.
Explanation:In order to understand which solution has the highest freezing point, think about a concept called freezing point depression. The freezing point depression is due to the number of solute particles in a given volume of solvent; more particles will result in a lower freezing point. The key to the number of particles is the van't Hoff factor (i), which shows how many particles a solute breaks up into when dissolved.
Selected solution (a) Ba(NO3)2 is a salt which breaks up into three ions in solution: Ba2+ and 2NO3-, so i=3. Solution (b) Mg(ClO4)2 also breaks up into three ions: Mg2+ and 2ClO4-, so i=3. Solution (c) HOCH2CH2OH, ethylene glycol, is a nonelectrolyte and doesn't ionize in solution, so i=1. Solution (d) Na3PO3 breaks up into four ions: 3Na+ and PO33-, so i=4.
Therefore, the solution with the highest freezing point will be the one that forms the fewest particles when dissolved, which is 0.200 m HOCH2CH2OH.
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The periodicity of the properties of elements is chiefly due to the
I) numbers of electrons in the atoms of the elements
II) distribution of electrons in the atoms of the elements
III) numbers of neutrons in the atoms of the elements
a) I only
b) I and III only
c) all of these
d) II only
e) III only
f) II and III only
g) none of these
h) I and II only
The periodic properties of elements are chiefly due to the numbers of electrons in each element's atoms and the distribution of these electrons. These properties don't significantly relate to the neutrons in the atoms. Thus, the correct answer is h) I and II only.
Explanation:The periodicity of the properties of elements is chiefly due to the numbers of electrons in the atoms of the elements and the distribution of electrons in the atoms of the elements. In the periodic table, these properties are mainly arranged by the atomic number of the elements, which determines the number of electrons, and their electronic configuration. More specifically, the arrangement is based on the number of protons (nuclear charge) and how the electrons are distributed in energy levels/shells around the nucleus.
So, the answer is h) I and II only.
The number of neutrons does not significantly affect periodic properties as the nature of an atom is primarily defined by its number of protons and electrons.
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Final answer:
The answer is (h) I and II only, where periodicity is primarily due to the number and distribution of electrons, which are related to the atomic number. The number of neutrons does not impact periodicity.
Explanation:
The periodicity of the properties of elements is chiefly due to the distribution of electrons in the atoms of the elements and the overall number of electrons, which correspond to their atomic number. The correct answer to the question is hence, option (h) I and II only. The number of protons in an atom (which is equivalent to the number of electrons in a neutral atom) and how these electrons are distributed among the different energy levels, or shells, determine the chemical and physical properties of an element.
Various properties such as atomic radius, ionization energy, and electron affinity can be understood through the element's position on the periodic table. Neutrons do not affect the chemical properties of elements and are thus irrelevant to periodicity. The specific arrangement of electrons, particularly in the outermost shells or valence shells, influences how an element reacts chemically and thus its placement in the periodic table.
A scientist adds a solution of HCl (aq) to a buffer comprised of CH3COOH (aq) and CH3COONa (aq). Which net ionic reaction would initially occur?
Explanation:
Net ionic between HCl and the buffer equation
CH3COOH --> acetic acid, CH3COO- acetate , H+ proton from HCl
there is neutralization of the acetate, and an increase in acid
the ionic equation
CH3COO-(aq) + H+(aq) + Cl-(aq) --> CH3COOH(aq) + Cl-(aq)
Net ionic:
CH3COO-(aq) + H+(aq) --> CH3COOH(aq).
Final answer:
H+ ions from added HCl react with the acetate ions in a buffer to form acetic acid, preventing a significant pH change.
Explanation:
When a strong acid like HCl is added to a buffer made of acetic acid (HC₂H₃O₂) and sodium acetate (CH₃COONa), the hydrogen ions (H+) from HCl will react with the acetate ions (C₂H₃O₂-) from sodium acetate in the buffer. The net ionic reaction for this process is:
H*(aq) + C₂H₃O₂-(aq) → HC₂H₃O₂(aq)
The reaction shows that H+ ions are intercepted by the buffer's acetate anions to form acetic acid (HC₂H₃O₂), preventing a significant change in pH and maintaining the buffer's purpose.
Which combination of characteristics is most likely to be associated with molecules having strong dipole-dipole interactions? I. polar bond II. asymmetric shape III. relatively low boiling point IV. large surface area
Answer:
I and II.
Explanation:
The interactions between the molecules in a substance are associated with the type of the substance. For ionic compounds, the atoms are joined together by the ion-ion interactions, for metallic compounds, by metallic interactions, and, for molecular compounds, they can be attracted by London forces, dipole-dipole forces or by hydrogen bonds.
The London forces exist in nonpolar molecules, which are the ones formed by nonpolar bonds (elements with the same electronegativity), or form bonds with the same polarity that is opposite, and so are canceled. The dipole-dipole force exists in polar molecules, and so, the atoms have partial charges, and the interactions are stronger than in London forces. If the dipole-dipole exists with hydrogen and a high electronegative element (N, O, or F), the bond is even strong and is called a hydrogen bond.
So, let's analyze the statements:
I. As said above, dipole-dipole occurs in polar molecules, so they may have polar bonds, and the statement is correct;
II. Because the polarity of the bonds is a vector when the shape is symmetric, is more likely to the polarities be canceled, so it's usual to the polar molecules be asymmetric, and the statement is correct;
III. Because the dipole-dipole is a strong force, it's difficult to break it and the substance needs more energy to change phase, so they have a high boiling point, and the statement is incorrect;
IV. Because the shape of the molecule is asymmetric, the surface area intends to be small, the atoms are distributed in a small place. If the molecule is linear, for example, then the atoms are distributed in large spaces, so the statement is incorrect.
A reaction has an equilibrium constant of 7.9×10³ at 298 K. At 713 K, the equilibrium constant is 0.77.
Do you predict that the enthalpy of the reaction is positive or negative? Why?
a. Positive, because endothermic reactions shift toward products at higher temperatures
b. Negative, because exothermic reactions shift toward reactants at higher temperatures
c. Positive, because endothermic reactions shift toward reactants at higher temperatures
d. Negative, because exothermic reactions shift toward products at higher temperatures
Answer:
option b is correct
Explanation:
Taking the Van't Hoff equation
d ln Keq / dT = ΔH/(RT²)
then
Keq increases with increasing temperature (d ln Keq / dT>0) when ΔH>0 and decreases with increasing temperature (d ln Keq / dT<0) when ΔH<0
if Keq decreases (reactions shift toward reactants) from 7.9×10³ to 0.77 when temperature increases from 298 K to 713 K (d ln Keq / dT<0) → ΔH<0 ( exothermic reaction)
therefore option b is correct
The enthalpy of the reaction is predicted to be negative, indicating it is an exothermic reaction, because the equilibrium constant decreases with an increase in temperature, a characteristic of exothermic reactions. Therefore, the correct answer is b.
The question asks if the enthalpy of the reaction is positive or negative based on changes in the equilibrium constant at different temperatures. The equilibrium constant decreases from 7.9×10³ at 298 K to 0.77 at 713 K. According to the principle that for an endothermic reaction (ΔH° > 0), the magnitude of K increases with increasing temperature, and conversely, for an exothermic reaction (ΔH° < 0), the magnitude of K decreases with increasing temperature, we can deduce the nature of the reaction. As the equilibrium constant decreases with an increase in temperature, the reaction must be exothermic. Therefore, the correct answer is b. Negative, because exothermic reactions shift toward reactants at higher temperatures.
A sample of gas occupies a volume of 10.5 L when the pressure is 14.3 psi. Use Boyle’s Law to calculate the pressure (psi) when the volume is reduced to 8.55L. Show the calculation.
Answer: 17.6psi
Explanation:
V1 = 10.5 L
P1 = 14.3 psi
V2 = 8.55L
P2 =?
P1V1 = P2V2
14.3 x 10.5 = P2 x 8.55
P2 = (14.3 x 10.5) / 8.55
P2 = 17.6psi
Answer:
The final pressure is 17.56 psi
Explanation:
Step 1: Data given
Initial volume = 10.5 L
Initial pressure = 14.3 psi
Final volume = 8.55 L
Step 2: Calculate the new pressure
P1V1 = P2V2
⇒ P1 = The initial pressure = 14.3 psi
⇒ V1 = The initial volume = 10.5L
⇒ P2 = The final pressure = TO BE DETERMINED
⇒ V2 = The final volume = 8.55 L
14.3 * 10.5 = P2*8.55
P2 = 17.56 psi
The final pressure is 17.56 psi