Answer:
13.5 g
Explanation:
This question is solved easily if we remember that the number of moles is obtained by dividing the mass into the atomic weight or molar mass depending if we are referring to elements or molecules.
Therefore, the mass of aluminum in the reaction will the 0.050 mol Al times the atomic weight of aluminum.
number of moles = n = mass of Al / Atomic Weight Al
⇒ mass Al = n x Atomic Weight Al = 0.050 mol x 27 g mol⁻¹
= 13.5 g
We have three significant figures in 0.050 and therefore we should have three significant figures in our answer.
Mass of aluminum that participated in the chemical reaction is 1.35 grams.
Number of Moles:
Number of moles is defined as the ratio of given mass to the molar mass.
Given:
Moles of Aluminum = 0.050 moles
To find:
Mass of Aluminum=?
As we know, Molar mass of Aluminum = 27g/mol
On substituting the values:
[tex]\text{Number of Moles}=\frac{\text{Given mass}}{\text{Molar mass}} \\\\ \text{Given mass}= \text{Number of Moles}*\text{Molar mass}\\\\ \text{Given mass}= 0.050*27\\\\ \text{Given mass}=1.35\text{ grams}[/tex]
Thus, the mass of aluminum that participated in the chemical reaction is 1.35 grams.
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A hydrogen atom in an excited state can be ionized with less energy than when it is in its ground state. What is n for a hydrogen atom if 0.544 eV of energy can ionize it?
Explanation:
It is known that formula for the ionization energy of hydrogen atom is as follows.
E = [tex]\frac{13.6 eV}{n^{2}}[/tex]
or, n = [tex]\sqrt{\frac{13.6}{E}}[/tex]
The value of energy is given as 0.544 eV. Therefore, we will calculate the value of n as follows.
n = [tex]\sqrt{\frac{13.6}{E}}[/tex]
= [tex]\sqrt{\frac{13.6}{0.544 eV}}[/tex]
= 5
Thus, we can conclude that n equals to 5 for a hydrogen atom if 0.544 eV of energy can ionize it.
Final answer:
The principal quantum number n of a hydrogen atom that requires 0.850 eV of energy to ionize from an excited state is 4. This is calculated using the formula for the energy levels of hydrogen, En = -13.6 eV/n², and solving for n.
Explanation:
The question relates to the energy levels of a hydrogen atom and how much energy is required to ionize it when the electron is in an excited state. The ionization energy of hydrogen in the ground state (n = 1) is 13.6 eV. To find the principal quantum number n for a particular amount of energy required to ionize the hydrogen atom from an excited state, we use the formula: En = -13.6 eV/n². We can set this equal to the energy needed to ionize the atom, in this case, 0.850 eV, and solve for n.
First, we rearrange the formula so it looks like this:
-13.6 eV/n² = -0.850 eV
Then we solve for n:
n² = 13.6 eV / 0.850 eV
n² = 16
n = √16
n = 4
Thus, the hydrogen atom is in the n = 4 excited state when 0.850 eV of energy can ionize it.
High-density polyethylene may be chlorinated by inducing the random substitution of chlorine atoms for hydrogen. Determine the concentration of Cl (in wt%) that must be added if this substitution occurs for 6% of all the original hydrogen atoms.
Explanation:
Let us assume that 50 carbon atoms are available with possible 100 site bondings. It is given here that 94% are occupied by hydrogen (94 out of 100) and 6% (6 out of 100) are occupied by chlorine atom.
Therefore, moles of carbon = 50
moles of hydrogen = 94
moles of chlorine = 6
Therefore,
Mass of 50 carbon atoms = [tex]50 \times 12.01 g/mol[/tex] = 600.5 g/mol
Mass of 94 hydrogen atoms = [tex]94 \times 1.008 g/mol[/tex] = 94.752 g/mol
Mass of 6 chlorine atoms = [tex]6 \times 35.45 g/mol[/tex] = 212.7 g/mol
Therefore, concentration of chlorine is as follows.
[tex]C_{cl} = \frac{m_{cl}}{m_{c} + m_{H} + m_{cl}}[/tex]
= [tex]\frac{212.7}{907.952} \times 100[/tex]
= 23.42%
thus, we can conclude that the concentration of Cl is 23.42%.
The calculation of Chlorine concentration in high-density polyethylene after 6% Hydrogen replacement involves determining the increased mass from Chlorine substitution, considering the significant difference in atomic masses of Hydrogen and Chlorine. Chlorine's contribution to the weight of the new compound would be considerable.
Explanation:High-density polyethylene has a chemical formula of (C2H4)n, where 'n' denotes the number of repeating units in the polymer chain. Each molecule of ethylene contributes two hydrogen atoms. Therefore, if we assume 6% of all hydrogen atoms are replaced by chlorine atoms, we have to add the weight of chlorine into the composition.
Under normal conditions, Chlorine (Cl) has an atomic weight of approximately 35.45 g/mol, and Hydrogen (H) has an atomic weight of approximately 1.008 g/mol. Therefore, the introduction of Chlorine substitutes a weight of 35.45 g for every 1.008 g of Hydrogen.
To calculate the weight percent of Chlorine in the composition, we determine the total weight contributed by chlorine and divide it by the total weight of the new compound, then multiply by 100%. As a result, the weight percentage of Chlorine when 6% of hydrogen atoms are replaced, following the calculations and the Principle of Atomic Substitution, is quite significant due to the considerable difference in atomic weights of Chlorine and Hydrogen.
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The rate of SN2 reaction of the type Nu- RX -> R-Nu X- can be increased Select one: a. using a solvent of high polarity b. using tertiary substrate c. using weak nucleophile d. using higher concentration of the nucleophile
Answer:
using higher concentration of the nucleophile
Explanation:
In SN2 reaction, the attack of the nucleophile on the substrate occurs simultaneously as the leaving group departs. The entering group normally attacks through the back side of the molecule. The reaction is concerted and bimolecular. This implies that the concentration of the nucleophile is important in the rate equation for the reaction. Hence increasing the concentration of the nucleophile will increase the rate of SN2 reaction.
The Fischer esterification mechanism is examined in the following two questions in the assignment. Part 1 involves MeOH addition to form the key tetrahedral intermediate. Part 2 will involve loss of H2O to form the ester. Part 1 of 2:
The Fischer esterification mechanism involves two main steps: the addition of methanol (MeOH) to a carboxylic acid to form a tetrahedral intermediate, and the loss of water (H2O) to create the ester.
Explanation:The Fourier esterification is a fundamental mechanism in Chemistry and encompasses two main steps. Part 1 involves the Addition of Methanol (MeOH) to a carboxylic acid to form a tetrahedral intermediate. Here, the lone pair of electrons on the oxygen of the MeOH attacks the carbonyl carbon of the acid, pushing the electrons up onto the carbonyl oxygen and forming the tetrahedral intermediate. Part 2 is the Loss of water (H2O) to create the ester. The hydroxyl group of the intermediate acts as a leaving group, departing as a water molecule. The lone pair of electrons on the oxygen then comes back down and forms the pi bond, hence forming the ester.
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In the Fischer esterification mechanism, a carboxylic acid and an alcohol react, leading to the formation of an ester and water. It's called a 'key tetrahedral intermediate' and the process involves the loss of a water molecule.
Explanation:The Fischer esterification mechanism is a fundamental process in organic chemistry that involves the transformation of a carboxylic acid and an alcohol into an ester. This process is initiated by the addition of an alcohol, such as MeOH (methanol), to the carboxylic acid via a nucleophilic attack, forming a tetrahedral intermediate.
The carboxylic acid group of this intermediate subsequently loses a water molecule (H2O) in a dehydration process, resulting in the formation of the desired ester.
For example, when ethanol reacts with acetic acid (ethanoic acid), the ester known as ethyl acetate (methyl ethanoate) is produced. Notably, esters are recognized for their fragrant odors, deriving from various plants and their fruits, such as honey methyl phenylacetate.
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How much heat is required to vaporize 31.5 gg of acetone (C3H6O)(C3H6O) at 25 ∘C∘C? The heat of vaporization for acetone at this temperature is 31.0 kJ/molkJ/mol.
Answer:
≅ 16.81 kJ
Explanation:
Given that;
mass of acetone = 31.5 g
molar mass of acetone = 58.08 g/mol
heat of vaporization for acetone = 31.0 kJ/molkJ/mol.
Number of moles = [tex]\frac{mass}{molar mass}[/tex]
Number of moles of acetone = [tex]\frac{31.5}{58.08}[/tex]
Number of moles of acetone = 0.5424 mole
The heat required to vaporize 31.5 g of acetone can be determined by multiplying the number of moles of acetone with the heat of vaporization of acetone;
Hence;
The heat required to vaporize 31.5 g of acetone = 0.5424 mole × 31.0 kJ/mol
The heat required to vaporize 31.5 g of acetone = 16.8144 kJ
≅ 16.81 kJ
Biphenyl, C 12 H 10 , C12H10, is a nonvolatile, nonionizing solute that is soluble in benzene, C 6 H 6 . C6H6. At 25 ∘ C, 25 ∘C, the vapor pressure of pure benzene is 100.84 Torr. What is the vapor pressure of a solution made from dissolving 10.3 g 10.3 g of biphenyl in 27.8 g 27.8 g of benzene?
Answer:
Vapor pressure of solution is 98.01 Torr
Explanation:
Colligative property. In this case, we apply the lowering vapor pressure.
ΔP = P° . Xm
P° - P' = Vapor pressure of pure solvent - Vapor pressure of solution = ΔP
Xm is the molar fraction for solute. We try to determine it:
Moles of solute / Total moles → Total moles = Solute moles + Solvent moles
10.3 g . 1mol / 154 g = 0.0669 moles of biphenyl
27.8 g . 1mol / 78 g = 2.32 moles of benzene
Total moles = 2.32 moles + 0.0669 moles = 2.3869 moles
Xm for solute = 0.0669 / 2.3869 = 0.028
Let's replace data:
100.84 Torr - P' = 100.84 Torr . 0.028
P' = - (100.84 Torr . 0.028 - 100.84Torr) = 98.01 Torr
Answer:
The vapor pressure of the solution is 84.9 torr
Explanation:
Biphenyl is a nonvolatile, nonionizing solute
Temperature = 25.0 °C
Vapor pressure = 100.84 torr
Mass of biphenyl = 10.3 grams
Mass of benzene = 27.8 grams
Molar mass biphenyl = 154.21 g/mol
Molar mass benzene = 78.11 g/mol
Step 2: Calculate moles
Moles = mass / molar mass
Moles biphenyl = 10.3 grams / 154.21 g/mol
Moles biphenyl = 0.0668 moles
Moles benzene = 27.8 grams / 78.11 g/mol
Moles benzene = 0.356 moles
Step 3: Calculate total moles
Total moles = 0.0668 moles + 0.356 moles
Total moles= 0.4228 moles
Step 4: Calculate mol fraction benzene
Mol fraction benzene = moles benzene / total moles
Mol fraction benzene = 0.356 moles / 0.4228 moles
Mol fraction benzene = 0.842
Step 5: Calculate vapor pressure of the solution
Psol = Xbenzene * P°benzene
⇒Psol = the vapor pressure of the solution
⇒Xbenzene = mol fraction of benzene
⇒P°benzene = the vapor pressure of pure benzene
Psol = 0.842 * 100.84 torr
Psol = 84.9 torr
The vapor pressure of the solution is 84.9 torr
Calculate the value of K p for the equation C ( s ) + CO 2 ( g ) − ⇀ ↽ − 2 CO ( g ) K p = ? given that at a certain temperature C ( s ) + 2 H 2 O ( g ) − ⇀ ↽ − CO 2 ( g ) + 2 H 2 ( g ) K p 1 = 3.23 H 2 ( g ) + CO 2 ( g ) − ⇀ ↽ − H 2 O ( g ) + CO ( g ) K p 2 = 0.693
Answer:
kp = 1.55
Explanation:
To get to this reaction, we just need to sum the other two reactions, and multiply coefficients if it's needed so:
C(s) + 2H₂O(g) ⇄CO₂(g) + 2H₂(g) Kp1 = 3.23 (1)
H₂(g) + CO₂(g) ⇄ H₂O(g) + CO(g) Kp2 = 0.601 (2)
we will multiply eqn 2 by 2 because we need to eliminate H₂
2H2(g) + 2CO2(g) ⇄ 2H2O(g) + 2CO(g) Kp = (0.601)²
Now, add both equation
C(s) + 2H₂O(g) ⇄CO₂(g) + 2H₂(g) Kp1 = 3.23
2H2(g) + 2CO2(g) ⇄ 2H2O(g) + 2CO(g) Kp = (0.601)²
we have,
C(s) + CO₂(g) ⇄ 2CO(g)
Now the value of Kp will be:
kp = 3.23 × (0.693)²
kp = 1.55
Select the correct definition of a glycolipid. A glycolipid is: a lipid molecule that contains a glycerol backbone and three fatty acids a lipid molecule that contains at least one carbohydrate unit a lipid molecule produced during glycolysis a molecule produced during the breakdown of glycogen
Answer:
a lipid molecule that contains at least one carbohydrate unit
Explanation:
A glycolipid -
It refers to the lipid which consists of the carbohyde group attached via a glycosidic bond , which are basically covalent bonds , is referred to as a glycolipid .
They are present on the surface of the eukaryotic cell membranes .
Glycolipids are important to connect from one tissue to another and facilitate cellular recognition .
Hence , from the given information of the question ,
The correct answer is a lipid molecule that contains at least one carbohydrate unit .
how many aluminum atoms are in 3.78g of aluminum?
Answer:
The molar mass of aluminum is 26.9 grams per mole. We start by converting the grams of aluminum to moles of aluminum.
m
o
l
A
l
=
3.78
g
A
l
×
1
m
o
l
A
l
26.9
g
=
0.1405
m
o
l
A
l
We use Avogadro's number to determine the number of aluminum atoms present in 0.1405 mol Al.
A
t
o
m
s
A
l
=
0.1405
m
o
l
A
l
×
6.022
×
10
23
1
m
o
l
A
l
=
8.46
×
10
22
a
t
o
m
s
A
l
Answer:
0.846×10²³
Explanation:
molar mass of aluminum is 26.9 g/mol.
converting the grams of aluminum to moles of aluminum.
mol Al = 3.78 g ×1 mol Al÷26.9 g = 0.1405 mol of Al
to determine the number of aluminum atoms present in 0.1405 mol Al we use the Avogrado's number which is equal to 6.022×10²³
Atoms of Al = 0.1405 mol Al×6.022×10²³
= 0.846×10²³
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For the oxidation–reduction reaction equation 2 Rb + Br 2 ⟶ 2 RbBr 2Rb+Br2⟶2RbBr indicate how many electrons are transferred in the formation of one formula unit of product.
For the given reaction between rubidium and Boron, only one electron will be transferred in the formation [tex]2 RbBr[/tex].
The potential difference between the two half-cells of an electrochemical cell is known as cell potential. The transfer of electrons from one-half cell to another produces the potential difference.
The given chemical reaction is:
[tex]2Rb_{(s)} + Br_{(l)}[/tex] ⇒ [tex]2RbBr_{(s)}[/tex]
The following electrochemical reaction can be divided into the reaction occurring at the cathode and the reaction occurring at the anode:
Oxidation reaction at the anode: [tex]2Rb_{(s)}[/tex] ⇒ [tex]2Rb^+_{(aq)} + 2e^-[/tex]
Reduction reaction at the cathode: [tex]Br_{2(l)} + 2e^-[/tex] ⇒ [tex]2Br^-_{(aq)}[/tex]
Since there are two units of RbBr in the aforementioned equation and two electrons were transported, only one electron is needed to generate one unit of RbBr.
Thus, only one electron is involved in the formation of RbBr.
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Final answer:
In the formation of one formula unit of RbBr, one electron is transferred from rubidium (Rb) to bromine (Br), as Rb loses one electron to form Rb+ and Br gains one electron to form Br-.
Explanation:
The question regards the number of electrons transferred in the formation of one formula unit of RbBr from the reaction 2 Rb + Br2 → 2 RbBr. In order to determine the electron transfer, we need to consider the oxidation states of the elements involved. Rubidium (Rb) is oxidized, meaning it loses electrons, and bromine (Br2) is reduced, meaning it gains electrons.
Rubidium starts with an oxidation state of 0 and becomes Rb+ in RbBr. This indicates that each Rb atom loses one electron. Bromine starts with an oxidation state of 0 as diatomic Br2 and each Br atom gains one electron to become Br- in RbBr. Therefore, for each RbBr formula unit produced, one electron is transferred from Rb to Br.
A chemist prepares a solution of pottasium bromide KBr by measuring out 224.g of pottasium bromide into a 300.mL volumetric flask and filling the flask to the mark with water. Calculate the concentration in mo/L of the chemist's pottasium bromide solution. Round your answer to 3 significant digits.
Explanation:
Below is an attachment containing the solution.
Answer:
The concentration of the KBr solution is 6.27 mol/L
Explanation:
Step 1: Data given
Mass of KBr = 224 grams
Molar mass KBr = 119.0 g/mol
Volume = 300 mL = 0.300 L
Step 2: Calculate moles KBr
Moles KBr = mass KBr / molar mass KBr
Moles KBr = 224 grams / 119.0 g/mol
Moles KBr = 1.88 moles
Step 3: Calculate concentration KBr solution
Concentration solution = moles KBr / volume
Concentration solution = 1.88 moles / 0.300 L
Concentration solution = 6.27 mol / L
The concentration of the KBr solution is 6.27 mol/L
In order to safely run a sample in a centrifuge, it is important to Select one: a. balance the sample with a counterweight of the same mass directly across from it. b. make sure the sample is free from impurities. c. ensure that the sample fills the centrifuge tube completely. d. do all of the given tasks.
Answer: Option (b) is the correct answer.
Explanation:
A laboratory device which is used to separate fluids, gases or liquid on the basis of their density is known as a centrifuge. When a vessel containing the sample is spins at a high speed then separation takes place as the centrifugal force pushes the heavier material out of the vessel during this process.
So, if we want the sample to safely run through the centrifuge then it is important that it should be free from impurities.
Thus, we can conclude that in order to safely run a sample in a centrifuge, it is important to make sure the sample is free from impurities.
When the safety run sample should be in a centrifuge so the sample should be free from impurities.
Laboratory device:It is used to distinguish gases or liquids that depend upon the density is called a centrifuge. At the time When a vessel comprised of the sample should be spinning at a high speed so the separation took place since the centrifugal force pushes the heavier material that should be out of the vessel at the time of the process.
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Compare the system (still at 50 °C) with a volume of 1.0 L and with 3.0 L. What is the total amount of gas (mol) present in the container at each of these volumes?
At a constant temperature of 50 °C, a volume of 1.0 L would contain approximately 0.045 moles of gas, whereas a volume of 3.0 L would contain approximately 0.134 moles of gas. These values are based on the standard molar volume of 22.4 L/mol at Standard Temperature and Pressure (STP).
Explanation:In order to make this comparison, we can use Avogadro's Law which states that equal volumes of gases, at the same temperature and pressure, will contain an equal number of molecules or moles. We would also use the standard molar volume of an ideal gas at Standard Temperature and Pressure (STP), which is about 22.4 L/mol.
Given that our system's temperature is constant at 50 °C and comparing volumes of 1.0 L and 3.0 L, we simply calculate the number of moles in each volume. For 1.0 L, if we stay consistent with molar volume at STP, it equates to about 0.045 moles of gas (1 L / 22.4 L per mole). For 3.0 L, it would equate to about 0.134 moles of gas (3 L / 22.4 L per mole).
Please note that this approximation is based on the standard molar volume at STP, and accuracy may vary at temperatures significantly different from STP (such as 50 °C).
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In the Haber reaction, patented by German chemist Fritz Haber in 1908, dinitrogen gas combines with dihydrogen gas to produce gaseous ammonia. This reaction is now the first step taken to make most of the world's fertilizer. Suppose a chemical engineer studying a new catalyst for the Haber reaction finds that liters per second of dinitrogen are consumed when the reaction is run at and. Calculate the rate at which ammonia is being produced.
The question is incomplete, complete question is :
In the Haber reaction, patented by German chemist Fritz Haber in 1908, dinitrogen gas combines with dihydrogen gas to produce gaseous ammonia. This reaction is now the first step taken to make most of the world's fertilizer. Suppose a chemical engineer studying a new catalyst for the Haber reaction finds that 348 liters per second of dinitrogen are consumed when the reaction is run at 205°C and 0.72 atm. Calculate the rate at which ammonia is being produced.
Answer:
The rate of production of ammonia is 217.08 grams per second.
Explanation:
[tex]N_2+3H_2\rightarrow 2NH_3[/tex]
Volume of dinitrogen used in a second = 348 L
Temperature of the gas = T = 205°C = 205+273 K = 478 K
Pressure of the gas = P = 0.72 atm
Moles of dinitrogen = n
[tex]n=\frac{PV}{RT}=\frac{0.72 atm\times 348 L}{0.0821 atm L/mol K\times 478 K}=6.385 mol[/tex]
According to reaction, 1 mole of dinitriogen gives 2 mole of ammonia.Then 6.385 moles of dinitrogen will give:
[tex]\frac{2}{1}\times 6.385 mol=12.769 mol[/tex]
Mass of 12.769 moles of ammonia;
12.769 mol 17 g/mol = 217.08 g
217.08 grams of ammonia is produced per second.So, the rate of production of ammonia is 217.08 grams per second.
A particular reaction, A- products, has a rate that slows down as the reaction proceeds. The half-life of the reaction is found to depend on the initial concentration of A. Determine whether each statement is likely to be true or false for this reaction.
a. A doubling of the concentration of A doubles the rate of the reaction.
b. A plot of 1/[A] versus time is linear.
c. The half-life of the reaction gets longer as the initial concen- tration of A increases.
d. A plot of the concentration of A versus time has a constant slope.
Explanation:
Half life of zero order and second order depends on the initial concentration. But as the given reaction slows down as the reaction proceeds, therefore, it must be second order reaction. This is because rate of reaction does not depend upon the initial concentration of the reactant.
a. As it is a second order reaction, therefore, doubling reactant concentration, will increase the rate of reaction 4 times. Therefore, the statement a is wrong.
b. Expression for second order reaction is as follows:
[tex]\frac{1}{[A]} =\frac{1}{[A]_0} +kt[/tex]
the above equation can be written in the form of Y = mx + C
so, the plot between 1/[A] and t is linear. So the statement b is true.
c.
Expression for half life is as follows:
[tex]t_{1/2}=\frac{1}{k[A]_0}[/tex]
As half-life is inversely proportional to initial concentration, therefore, increase in concentration will decrease the half life. Therefore statement c is wrong.
d.
Plot between A and t is exponential, therefore there is no constant slope. Therefore, the statement d is wrong
Liquid hexane will react with gaseous oxygen to produce gaseous carbon dioxide and gaseous water . Suppose 9.48 g of hexane is mixed with 43. g of oxygen. Calculate the minimum mass of hexane that could be left over by the chemical reaction. Be sure your answer has the correct number of significant digits.
Answer:
No mass of hexane could be left over by the chemical reaction.
C₆H₁₄ is the limitin reagent
Explanation:
This is a combustion reaction were the oxygen is one of the reactant and it burns a compound in order to generate water and carbon dioxide.
In this case, we have liquid hexane combustion, so the reaction is:
2C₆H₁₄(l) + 19O₂(g) → 12CO₂(g) + 14H₂O(g)
In this situation we are asked for the mass of a reactant that could be left over, this is the excess reagent.
We convert the masses of reactants to moles:
9.48 g . 1mol / 86g = 0.110 moles of C₆H₁₄
43 g . 1 mol/32 g = 1.34 moles of O₂
The hexane may be the excess reagent but we confirm like this:
19 moles of O₂ need 2 moles of hexane to react
Then, 1.34 moles of O₂ will react with (1.34 . 2) / 19 = 0.141 moles
We need 0.141 moles, and we only have 0.110. Hexane is the limiting reagent so no mass could be left over by the chemical reaction.
In conclussion, oxygen is excess reactant. We verify:
2 moles of hexane need 19 moles of O₂ to react
Then, 0.110 moles of hexane will react with (0.110 . 19) / 2 = 1.04 moles of O₂
As I have 1.34 moles of oxygen, value is higher so in this case we are having mass that could be left over by the reaction.
Write the expression for the equilibrium constant for the reaction represented by the equation CaCO3(s)⇌Ca2+(aq)+CO32−(aq). Is Kc > 1, < 1, or ≈ 1? Explain your answer.
Answer: For the given reaction, the value of [tex]K_c[/tex] is greater than 1
Explanation:
For the given chemical equation:
[tex]CaCO3(s)\rightleftharpoons Ca^{2+}(aq.)+CO_3^{2-}(aq.)[/tex]
The expression of [tex]K_c[/tex] for above equation follows:
[tex]K_c=\frac{[Ca^{2+}]\times [CO_3^{2-}]}{[CaCO_3}]\\\\K_c=[Ca^{2+}]\times [CO_3^{2-}][/tex]
The concentration of pure solids and pure liquids are taken as 1 in equilibrium constant expression
As, the denominator is missing and the numerator is the only part left in the expression. So, the value of [tex]K_c[/tex] will be greater than 1.
Hence, for the given reaction, the value of [tex]K_c[/tex] is greater than 1
Given the reactions below, (1) Na(s) + H2O(l) → NaOH(s) + 1/2 H2(g) LaTeX: \Delta H^o_{rxn}Δ H r x n o = −146 kJ (2) Na2SO4(s) + H2O(l) → 2NaOH(s) + SO3(g) LaTeX: \Delta H^o_{rxn}Δ H r x n o = 418 kJ (3) 2Na2O(s) + 2H2(g) → 4Na(s) + 2H2O(l) LaTeX: \Delta H^o_{rxn}Δ H r x n o = 259 kJ Determine LaTeX: \Delta H^o_{rxn}Δ H r x n o for the following reaction: (4) Na2O(s) + SO3(g) → Na2SO4(s) LaTeX: \Delta H^o_{rxn}Δ H r x n o = ?
Answer:
ΔrxnH = -580.5 kJ
Explanation:
To solve this question we are going to help ourselves with Hess´s law.
Basically the strategy here is to work in an algebraic way with the three first reactions so as to reprduce the desired equation when we add them together, paying particular attention to place the reactants and products in the order that they are in the desired equation.
Notice that in the 3rd reaction we have 2 mol Na₂O (s) which is a reactant but with a coefficient of one, so we will multiply this equation by 1/2-
The 2nd equation has Na₂SO₄ as a reactant and it is a product in our required equation, therefore we will reverse the 2nd . Note the coefficient is 1 so we do not need to multiply.
This leads to the first equation and since we need to cancel 2 NaOH, we will nedd to multiply by 2 the first one.
Taking 1/2 eq 3 + (-) eq 2 + 2 eq 1 should do it.
Na₂O (s) + H₂ (g) ⇒ 2 Na (s) + H₂O(l) ΔrxnHº = 259 / 2 kJ 1/2 eq3
+ 2NaOH(s) + SO₃(g) ⇒ Na₂SO₄ (s) + H₂O (l) ΔrxnHº = -418 kJ - eq 2
+ 2Na (s) + 2 H₂O (l) ⇒ 2 NaOH (s) + H₂ (g) ΔrxnHº = -146 x 2 2 eq 1
Na₂O (s) + SO₃ (g) ⇒ Na₂SO₄ (s) ΔrxnHº = 259/2 + (-418) + (-146) x 2 kJ
ΔrxnH = -580.5 kJ
Final answer:
To find the enthalpy change for the reaction Na2O(s) + SO3(g) → Na2SO4(s), we apply Hess's Law and manipulate the given reactions to find that the enthalpy change is -288.5 kJ.
Explanation:
To determine the enthalpy change (\(\Delta H^o_{rxn}\)) for the reaction (4) Na2O(s) + SO3(g) → Na2SO4(s), we use Hess's Law which states that if a reaction is the sum of two or more other reactions, the enthalpy changes of the constituent reactions can be added to determine the enthalpy change of the overall process. We need to find a combination of reactions (1), (2), and (3) that will result in reaction (4).
Here are the given reactions with their enthalpy changes:
Na(s) + H2O(l) → NaOH(s) + 1/2 H2(g), \(\Delta H^o_{rxn} = -146 kJ\)
Na2SO4(s) + H2O(l) → 2NaOH(s) + SO3(g), \(\Delta H^o_{rxn} = +418 kJ\)
2Na2O(s) + 2H2(g) → 4Na(s) + 2H2O(l), \(\Delta H^o_{rxn} = +259 kJ\)
To solve for the enthalpy of reaction (4), we need to reverse reaction (2) and halve reaction (3) to cancel out unwanted substances and leave Na2O(s) + SO3(g) on the left-hand side and Na2SO4(s) on the right-hand side.
Reversed reaction (2):\[\text{Na2SO4(s) + H2O(l) → 2NaOH(s) + SO3(g)}\], \(\Delta H^o_{rxn} = -418 kJ\) (since we reversed it)
Halved reaction (3):\[\text{Na2O(s) + H2(g) → 2Na(s) + H2O(l)}\], \(\Delta H^o_{rxn} = +259 kJ / 2 = +129.5 kJ\) (since we halved it)
Finally, we add the modified reaction (2) and (3):
(4) Na2O(s) + SO3(g) → Na2SO4(s), the enthalpy change is \(\Delta H^o_{rxn} = (-418 kJ) + (+129.5 kJ) = -288.5 kJ\).
Solvents at disposal:
Hexanes, Toluene, dichloromethane, diethyl, ethyl acetate, methanol, water, acetic acid
From the solvents, choose a single solvent that would give the best chance of separating benzophenone, diphenyl methanol and biphenyl using TLC on silica gel. Explain reasoning behind the choice. (phenyl groups are fairly non-polar)
Explanation:
In the given solvents -
Hexanes, Toulene, and dichloromethane have lesser eluting power. Diethyl ether and Ethyl acetate have medium eluting power. Methanol, water, and acetic acid have very little eluting power. Greater is the eluting power of the solvent lesser is the amount to be added. For solvents like Diethyl ether and Ethyl acetate have to be added in the percentage of 1% - 50% in addition to the solvent of higher eluting power. Hexanes and Toulene are often used in TLC (Thin Layer Chromatography ) as a Base. The reason behind this is they are non-polar compounds. The best-used solvent is Hexane.Final answer:
Toluene is the best solvent choice for separating benzophenone, diphenyl methanol, and biphenyl using TLC on silica gel due to its balanced polarity, which will allow for better differentiation between the non-polar compounds.
Explanation:
In choosing a solvent for separating benzophenone, diphenyl methanol, and biphenyl using TLC on silica gel, toluene appears to be the most appropriate choice. Since phenyl groups are fairly non-polar, a non-polar or moderately polar solvent is needed to achieve good separation. Toluene is a good choice because it has a higher polarity than hexanes but is less polar than the other solvents listed, providing a balanced environment to distinguish the three compounds on the basis of their differing polarities. A solvent like methanol or water would be too polar, causing the compounds to stay near the baseline, while hexanes might be too non-polar, failing to separate the compounds efficiently. Therefore, toluene is the recommended solvent for TLC in this scenario.
Be sure to answer all parts. A buffer consists of 0.38 M KHCO3 and 0.71 M K2CO3. Carbonic acid is a diprotic acid with Ka1 = 4.5 × 10−7 and Ka2 = 4.7 × 10−11. (a) Which Ka value is more important to this buffer?
Explanation:
The dissociation equations for the carbonic acid are as follows.
[tex]H_{2}CO_{3}(aq) + H_{2}O(l) \rightarrow HCO^{-}_{3}(aq) + H_{3}O^{+}(aq)[/tex]
[tex]HCO^{-}_{3}(aq) + H_{2}O(l) \rightarrow (CO^{2-}_{3})(aq) + H_{3}O^{+}(aq)[/tex]
The given buffer contains [tex]KHCO_{3}[/tex] and [tex]K_{2}CO_{3}[/tex]. This means that there will be [tex]HCO^{-}_{3}[/tex] ions and [tex]CO^{2-}_{3}[/tex] ions and since, both of them are present in the second step.
Therefore, [tex]K_{a2}[/tex] is more significant with respect to this reaction.
Thus, we can conclude that [tex]K_{a2}[/tex] is more important to this buffer.
A buffer resists changes in pH. When considering carbonic acid, which is a diprotic acid i.e., it can donate two protons, the first ionization is represented by Ka1, and the second by Ka2. In a buffer solution with physiological pH close to 7, Ka1 is more important because the first ionization of carbonic acid happens more readily at this pH.
Explanation:Your question asks which Ka value is more important for this buffer, which contains 0.38 M KHCO3 and 0.71 M K2CO3. Carbonic acid is a diprotic acid with Ka1 = 4.5 × 10^−7 and Ka2 = 4.7 × 10^−11.
A buffer solution resists changes in pH by neutralizing added acids and bases. The effectiveness of a buffer is determined by the pKa of the acid component of the buffer, which is the negative logarithm of its Ka. Generally, the most effective buffers are those wherein the pKa is close to the desired pH.
In our case, since carbonic acid is diprotic it has two associated Ka values. The first dissociation (giving HCO3^-) has Ka1 and the second dissociation (giving CO3^2-) has Ka2. Typically in physiological circumstances such as in our blood, where pH is close to 7, the first ionization of carbonic acid matters more because it is the one that happens readily at physiological pH. Therefore, Ka1 would be more important in this buffer solution as it represents the first ionization of the acid.
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An open tubular gas chromatography column is 35.7 m long and has an inner diameter of 0.250 mm. It is coated on the inside wall with a layer of stationary phase that is 1.8 µm (0.0018 mm) thick. Unretained solute, methane, passes through in 6.39 min, whereas toluene has a retention time of 16.35 min. Calculate the retention factor for toluene.
Answer:
The retention factor, k is 2.49
Explanation:
According to the theory of High-Performance Liquid Chromatography (HPLC), the retention factor (or capacity), k, of a column is the ratio of the retention time of a retained analyte (toluene) to that of the un-retained solute (methane).
This implies that:
k = [tex]\frac{16.35 (mins)}{ 6.39 (mins)}[/tex] = [tex]\frac{995 (secs)}{399 (secs)}[/tex]
retention factor, k = 2.49.
Note that there is no unit for retention factor, as it is a ratio.
Final answer:
The retention factor for toluene in the given gas chromatography system, calculated using the retention times of toluene and methane, is approximately 1.56.
Explanation:
The question involves calculating the retention factor (k) for toluene using gas chromatography (GC) data. The retention time is the time a compound spends in the column before being detected, which varies by compound owing to differences in interaction with the stationary phase. The retention factor is a measure of this time relative to an unretained solute, providing insight into the compound's affinity for the stationary phase versus the mobile phase.
To calculate the retention factor (k) for toluene, we use the formula: k = (t-R - t-M) / tM, where tR is the retention time of the analyte (toluene) and tM is the retention time of an unretained solute (methane, in this case). For toluene, t-R = 16.35 min, and for methane, t-M = 6.39 min. Substituting these values into the equation, we find k for toluene as follows: k = (16.35 - 6.39) / 6.39 = 9.96 / 6.39 ≈ 1.56.
Mirex(MW = 540) is a fully chlorinated organic pesticide that was manufactured to control fire ants. Due to its structure, mirex is very unreactive; thus, it persists in the environment. Lake Erie water samples have had mirex measured as high as 0.002 μg/L and lake trout samples with 0.002 μg/g. (a) (10 points) In the water samples, what is the aqueous concentration of mirex in units of (i) ppb, (ii) ppt, (iii) μM? (b) (10 points) In the fish samples, what is the concentration of mirex in (i) ppm, (ii) pp
Answer:
A) i) 0.002 ppb (ii) 2ppt (iii) 3.7 x 10^(-6) μM
B) i)0.002 ppm. (ii) 2ppb
Explanation:
A) We know that 1 ppb = 1 μgram per liter, and so the concentration of Mirex in ppb would be 0.002 ppb.
1 ppt = 1 nanogram per liter of water, so the concentration of Mirex in ppt would be 2 ppt;
(0.002 μg/L) (100ng/μg) (1ppt/ng/L) = 2ppt.
Now, MW of Mirex = 540 g/mol ≡ μg/μmol
Thus, 1 μmole = 540 μgram,
Hence, the concentration of Mirex in μmoles would be;
(0.002 μg/L)/(540 μg/μmol) = 3.7 x 10^(-6) μM
B) i) 1 ppm = 1 μgram per gram.
Thus, the concentration of Mirex in ppm would be = 0.002 ppm.
ii) Now, 1 ppb = 1 nanogram per gram.
Thus, concentration of Mirex in ppb would be = (0.002 μg/g) (100ng/μg) (1ppb ng/g) = 2ppb
Final answer:
The concentration of mirex in water samples is 0.002 ppb, 2 ppt, and approximately 3.70 x 10⁻³ μM. In fish samples, the concentration of mirex is 0.002 ppm and 2 ppb.
Explanation:
The student is asking about converting the concentration of a pesticide, mirex, in water and fish samples to various units. The concentration in water samples is given as 0.002 μg/L. The conversions are as follows:
Parts per billion (ppb) is equivalent to micrograms per liter (μg/L), so the concentration is 0.002 ppb.To convert to parts per trillion (ppt), we multiply the ppb value by 1,000. Thus, the concentration is 2 ppt.The concentration in micromolar (μM) can be found by dividing the microgram concentration by the molecular weight of mirex and then dividing by the volume of the solution in liters. Since the molecular weight (MW) of mirex is 540 g/mol, the calculation is 0.002 μg/L × (1 mg/1,000 μg) × (1 mol/540,000 mg) × (1,000,000 μM/1 M), resulting in approximately 3.70 x 10⁻³ μM.For the fish samples:
The concentration as parts per million (ppm) is the same as micrograms per gram (ug/g), so it is 0.002 ppm.The parts per billion (ppb) value is 0.002 ppb, as 1 ppm is equal to 1,000 ppb, and the value for mirex in fish is already less than 1 ppm.At the end of the isomerization reaction, what chemical is used to quench the residual bromine?At the end of the isomerization reaction, what chemical is used to quench the residual bromine?
Answer: Cyclohexene
Explanation:
Cyclohexane belongs to the Alkenes family. Alkenes react in the cold with pure liquid bromine, or with a solution of bromine in an organic solvent like tetrachloromethane. The double bond breaks, and a bromine atom get attached to each carbon. The bromine loses its original red-brown color to give a colorless liquid. In the case of the reaction with ethene, 1,2-dibromoethane is formed. When bromine is added to cyclohexane in the dark room, there won't be any reaction. If the mixture is exposed to light however, free bromine radicals are generated. In this condition, polybrominated products can be produced as well.
The chemical used to quench the residual bromine at the end of the isomerization reaction is usually an organic compound containing a reducing agent, such as sodium bisulfite (NaHSO3) or sodium hydrogen sulfite (NaHSO3).
Explanation:The chemical used to quench the residual bromine at the end of the isomerization reaction is usually an organic compound containing a reducing agent, such as sodium bisulfite (NaHSO3) or sodium hydrogen sulfite (NaHSO3). These compounds react with bromine to form non-toxic salts that can be easily removed. For example, NaHSO3 reacts with bromine to form sodium bromide (NaBr) and sodium sulfate (Na2SO4). This reaction effectively removes the residual bromine and prevents it from causing further reactions or harming the desired product.
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Explain in detail the differences & similarities between Fission & Fusion
Fusion and Fission both are nuclear reactions where the major difference between them is Fusion is combining process whereas fission is a breaking process.
Explanation:
Similarity:
Both Fission and Fusion are nuclear reactions that releases vast amount of energy.
Difference:
Fission is the splitting of heavier nucleus into lighter nuclei which generates maximum amount of energy whereas fusion is the combining 2 lighter nuclei to form a heavier nucleus and makes a vast energy. The energy generated by fission reaction in these reactors heats up the water into steam. This steam is utilized to rotate a turbine to generate carbon-free electricity. Fusion reactions are difficult to retain for longer period of time since it needs tremendous amount of temperature and pressure to combine the nuclei together.A sample of 9.49 g of solid calcium hydroxide is added to 30.0 mL of 0.490 M aqueous hydrochloric acid. Write the balanced chemical equation for the reaction. Physical states are optional.
Answer:
Ca(OH)2(s) + 2HCl(aq) → CaCl2(aq) + 2H2O(l)
Explanation:
Step 1: Data given
Mass of Ca(OH)2 = 9.49 grams
Volume of a 0.490 M HCl solution = 30.0 mL = 0.030 L
Step 2: The unbalanced equation
Ca(OH)2 + HCl → CaCl2 + H2O
On the left side we have 2x O (in Ca(OH)2 ) and on the right side we have 1x O (in H2O). To balance the amount of O we have to multiply H2O, on the right side , by 2.
Ca(OH)2 + HCl → CaCl2 + 2H2O
On the right side we have 4x H (in 2H2O), and on the left side we have 3x H (2x in Ca(OH)2 and 1x in HCl). To multiply the amount of H, we have to multiply HCl on the left side by 2.
Ca(OH)2(s) + 2HCl(aq) → CaCl2(aq) + 2H2O(l)
Spray drying_______________.a. converts solid foods to semi-solid foods b. atomizes liquids into small solid particles c. increases moisture content d. is similar to fluidized bed drying
Answer:
b. atomizes liquids into small solid particles
Explanation:
Spray drying -
It refers to the process of getting a dry powder from the liquid or the slurry ,with the help of hot gas , is referred to as spray drying .
The method is used in the field of pharmacy .
It is a type of atomizer or spray nozzle which helps to disperse the liquid into the controlled drop size spray .
Small solid particles are generated by this method .
Hence , from the given scenario of the question ,
The correct answer is b. atomizes liquids into small solid particles .
You want to determine the protein content in milk with the Kjeldahl method. You take 100 g whole milk and use 100 mL of 0.5 M hydrochloric acid to collect ammonia. You needed 34.50 mL of 0.3512 M NaOH for the back-titration. Calculate the percentage of protein in the sample?
Answer:
82.53 % protein in the milk.
Explanation:
Titration formula:
Conc (acid) × Vol (acid) = Conc (base) × Vol (base)
Beginning from back-titration:
0.5 M HCl × Vol (HCl) = 0.3512 (conc of NaOH) × 34.50 mL (vol of NaOH)
= [tex]\frac{12.1164}{0.5}[/tex] = 24.2328 mL
⇒ Vol of HCl used in initial titration is 24.2328 mL
So from Initial Titration:
Using same titration formula,
0.5 × 24.2328 = Conc. (base) × 100 ml
Conc (base) = 12.1164 ÷ 100
= 0.121164 M.
But concentration = mass ÷ molar mass
0.121164 = [tex]\frac{100 g}{ molar mass}[/tex]
= 825.3277 g/mol of protein
⇒ [tex]\frac{825.32765}{1000}[/tex] × 100
= 82.53 % protein in the milk.
A breeder nuclear reactor is a reactor in which nonfissile U-238 is converted into fissile Pu-239. The process involves bombardment of U-238 by neutrons to form U-239 which then undergoes two sequential beta decays. Write nuclear equations to represent this process.
Answer: The nuclear equations for the given process is written below.
Explanation:
The chemical equation for the bombardment of neutron to U-238 isotope follows:
[tex]_{92}^{238}\textrm{U}+n\rightarrow _{92}^{239}\textrm{U}[/tex]
Beta decay is defined as the process in which neutrons get converted into an electron and a proton. The released electron is known as the beta particle.
[tex]_Z^A\textrm{X}\rightarrow _{Z+1}^A\textrm{Y}+_{-1}^0\beta[/tex]
The chemical equation for the first beta decay process of [tex]_{92}^{239}\textrm{U}[/tex] follows:
[tex]_{92}^{239}\textrm{U}\rightarrow _{93}^{239}\textrm{Np}+_{-1}^0\beta[/tex]
The chemical equation for the second beta decay process of [tex]_{93}^{239}\textrm{Np}[/tex] follows:
[tex]_{93}^{239}\textrm{Np}\rightarrow _{94}^{239}\textrm{Pu}+_{-1}^0\beta[/tex]
Hence, the nuclear equations for the given process is written above.
A certain metal M crystallizes in a lattice described by a body-centered cubic (bcc) unit cell. The lattice constant (a, the edge of the unite cell) has been measured by X-ray crystallography to be 360. pm. Calculate the radius of an atom of M. Be sure your answer has 3 significant digits, and be sure it has the correct unit symbol.
Answer:
radius = 156 pm
Explanation:
The relation between radius and edge length of unit cell of BCC is
r=a[tex]\sqrt{3}[/tex]/4
Given
a = 360 pm
Therefore
r = r = radius = 360[tex]\sqrt{3}[/tex]/4= 155.88 pm
Or
156 pm
Cyclohexane (C6H12) is a hydrocarbon (a substance containing only carbon and hydrogen) liquid. Which of the following will most likely dissolve in cyclohexane to form a solution?
a) NaBr
b) CH2Cl2
c) CH3CH2CH2CH2CH3
d) HI
Answer: Option (c) is the correct answer.
Explanation:
It is known that like dissolves like. As cyclohexane is a hydrocarbon and we know that hydrocarbons are non-polar in nature. So, a non-polar compound will be soluble in a hydrocarbon.
For example, NaBr is an ionic compound and when it i added to liquid cyclohexane then it will not dissolve. Similarly, [tex]CH_{2}Cl_{2}[/tex] and HI are polar covalent compounds and they will not dissolve in liquid cyclohexane.
But [tex]CH_3CH_2CH_2CH_2CH_3[/tex] is a non-polar compound. So, when it is added to liquid cyclohexane then it will readily dissolve.
Thus, we can conclude that pentane ([tex]CH_3CH_2CH_2CH_2CH_3[/tex]) will most likely dissolve in cyclohexane to form a solution.