Answer:
A. 256
Explanation:
In a solution where a liquid is the sovent, we'll use the van't Hoff factor, which is the ratio between the number of moles of particles produced in solution and the number of moles of solute dissolved, will be equal to 1.
ΔTemp.f = i * Kf * b
where,
ΔTemp.f = the freezing-point depression;
i = the van't Hoff factor
Kf = the cryoscopic constant of the solvent;
b = the molality of the solution.
So the freezing-point depression by definition is the difference between the the freezing point of the pure solvent and the freesing point of the solution.
Mathematically,
ΔTemp.f = Temp.f° - Temp.f
where,
Temp.f° = the freezing point of the pure solvent.
Temp.f = the freezin point of the solution.
Freezing point of pure water = 0°C
ΔTemp.f = 0 - (-1.32)
= 1.32°C
i = 1,
Kf = 1.86 °Ckg/mol
Solving for the molality, b = ΔTemp.f/( i * Kf)
= 1.32/(1*1.86)
= 0.71 mol/kg
Converting from mol/kg to mol/g,
0.71 mol/kg * 1kg/1000g
= 0.00071 mol/g.
Mass of solvent = 110g
Number of moles = mass * molality
= 0.00071 * 110
= 0.078 mol.
To calculate molar mass,
Molar mass (g/mol) = mass/number of moles
Mass of solute (liquid) = 20g
Molar mass = 20/0.078
= 256.2 g/mol
A solution containing 20.0 g of an unknown liquid (molar mass 256 g/mol) and 110.0 g water has a freezing point of -1.32 °C.
What is the freezing point depression?Freezing point depression is a colligative property observed in solutions that results from the introduction of solute molecules to a solvent.
Step 1: Calculate the molality of the solution.We will use the following expression for non-electrolytes.
ΔT = Kf × b
b = ΔT/Kf = 1.32 °C/(1.86 °C/m) = 0.710 m
where,
ΔT is the freezing point depression.Kf is the cryoscopic constant.b is the molality.Step 2. Calculate the molar mass of the unknown liquid (solute).We will use the definition of molality.
b = mass solute / molar mass solute × kg solvent
molar mass solute = mass solute / b × kg solvent
molar mass solute = 20.0 g / (0.710 mol/kg) × 0.1100 kg = 256 g/mol
A solution containing 20.0 g of an unknown liquid (molar mass 256 g/mol) and 110.0 g water has a freezing point of -1.32 °C.
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Minerals are _________ inorganic _________ that usually possess a crystalline structure and can be represented by a chemical formula.
a) synthetic; solids
b) synthetic; liquids
c) naturally occurring; solids
d) naturally occurring; liquids
e) both naturally occurring and synthetic; solids
Answer:
The corect answer is c) naturally occurring; solids
Explanation:
Minerals exists as solid substances in nature consisting of one or more element chemically combined together formiming compounds with definite composition. As mentioned earlier single elements can form minerals and examples of single element mineral are Silver, Carbon and Gold which are found in nature in their pure form and are mined.
Minerals are normally found in rocks, which may contain one ore more different types of minerals
The gears on a bicycle are an example of what type of simple machine?
Lever
Wheel and Axle
Inclined plane
Pulley
The gears on a bicycle are an example of the wheel and axle type of simple machine, which includes a rod (axle) attached to the center of a wheel to amplify force or speed, and combines with levers and pulleys in the full mechanism of the bicycle.
The gears on a bicycle are an example of the wheel and axle type of simple machine. This particular type of simple machine consists of a rod (the axle) fixed to the center of a wheel, which together can amplify force or speed. Though similar to a lever, the wheel and axle design allows for continuous rotational motion, which is ideal for bicycles. According to renaissance scientists, there are six classifications of simple machines, which are the lever, wheel and axle, pulley, inclined plane, wedge, and screw. Bicycles actually combine several types of simple machines, including wheel and axles, levers, and in some cases, pulleys.
A gas in a balloon at constant pressure has a volume of 185 mL at -125*C. What is its volume at 31.0*C? Show all work including what equation or gas law you use.
Answer:
380 mL is the new volume
Explanation:
At constant pressure.
V₁ / T₁ = V₂ / T₂
Temperature must be in Absolute Values (T°K = T°C + 273)
-125°C + 273 = 148 K
31°C + 273 = 304 K
185 mL / 148 K = V₂ / 304 K
V₂ = (185 mL / 148 K) . 304 K → 380 mL
Patrice walks 4.0 blocks east and then turns north and jogs 6.0 blocks. She then turns west and walks another 4.0 blocks. What is the distance she has traveled?
0.0 blocks
8.0 blocks
6.0 blocks
14.0 blocks
Answer:
14.0 blocks
Explanation:
Distance travelled
= 4.0 blocks + 6.0 blocks + 4.0 blocks
= 14.0 blocks
Patrice has travelled 14.0 blocks.
Classify the following as either a heterogeneous or homogeneous mixture. Explain your answers. a. orange juice b. tap water
Answer :
(a) Orange juice → Heterogeneous mixture
(b) Tap water → Homogeneous mixture
Explanation:
Homogeneous mixture:
It is a type of mixture in which the components of the mixture are distributed uniformly throughout the mixture.
It can not be separated by physically. It has only one phase.
Heterogeneous mixture:
It is a type of mixture in which all the components are completely mixed and the particles present in the mixture can be separated by physically.
They have two or more phase.
From the given options, tap water is a homogeneous mixture because it has only one phase.
While the other options, orange juice are heterogeneous mixture because it can be separated by physically and they have two or more phase.
Tap water is a homogeneous mixture because its composition is uniformly distributed and it appears as one substance. Orange juice, especially if it contains pulp, is a heterogeneous mixture since its components (pulp and liquid) are distinct and not uniformly mixed.
Explanation:The substances in question, orange juice and tap water, can be classified as either homogeneous or heterogeneous mixtures. In a homogeneous mixture, the components are evenly mixed throughout and you can't see the different parts. Tap water is an example of this because it usually contains many different substances dissolved inside it like minerals, and gasses, but it still retains the same properties throughout, meaning it looks like one substance.
On the other hand, a heterogeneous mixture contains components that aren't evenly mixed and you can see the different parts. Orange juice, especially if it's freshly squeezed and contains pulp, is an example of a heterogeneous mixture. The pulp and liquid are very different in terms of texture and appearance and they don't blend into a single, indistinguishable mixture.
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Arrange the listed ions in increasing order of strength of reducing agent.
Aluminum:
Cobalt:
Copper:
Chromium:
Mercury:
Silver
Answer:
Arrange the listed ions in increasing order of strength of reducing agent.
Aluminum: 6
Cobalt: 4
Copper: 3
Chromium: 5
Mercury: 1
Silver: 2
Answer: 6, 4, 3 , 5 , 1 , 2
Aluminum: 6
Cobalt: 4
Copper: 3
Chromium: 5
Mercury: 1
Silver: 2
Explanation:
A minerals luster is produced by its ability to transmit light. Opaque minerals always have a metallic luster because they do not transmit any light. True False
Explanation:
The above statement is incorrect. The luster in minerals is not because of the their ability to transmit light but the ability to reflect light from their surface. More, the clean or polished the surface would be more light they would reflect.
Moreover, opaque minerals do not transmit light, they reflect it back into our eyes that is why we can see them. So, this correct.
Answer: nonmetallic; do not transmit
Explanation:
What factors affect the rate of a chemical reaction?
Answer:
The answer to your question is below
Explanation:
Factors that affect the rate of a chemical reaction
- Temperature If the temperature increases the rate of reaction increases.
- Concentration The reaction will move where there less concentration it could be to the reactants of products.
- Particle size The lower the particle size the higher the rate of reaction.
- Catalyst Catalyzers accelerate the rate of reaction
- Pressure The reaction will move where there are fewer molecules.
Final answer:
The rate of a chemical reaction is affected by the chemical nature of reactants, surface area, temperature, concentration, and the presence of a catalyst.
Explanation:
Factors Affecting the Rate of Chemical Reactions
The rate at which a chemical reaction proceeds can be influenced by various factors. Primary among these are the chemical nature of the reactants, the surface area, the temperature of the system, the concentration of reactants, and the presence of a catalyst. The chemical nature determines how reactive a substance is. The surface area comes into play particularly when reactants are in different phases; smaller particles or greater surface area contact typically speeds up reactions. Increasing the temperature usually causes reaction rates to increase because reactant molecules move faster and collide more often with enough energy to surmount the activation energy barrier. Similarly, higher reactant concentrations lead to more frequent collisions and a higher reaction rate. Lastly, a catalyst can provide an alternative reaction pathway with a lower activation energy, thus increasing the reaction rate without being consumed in the process.
Based upon elemental analysis, the empirical formula for an unknown compound was calculated to be CH2. Mass spectrometry analysis reveals the compound to have a molar mass of approximately 42 g/mol. What is the molecular formula for the compound
Answer:
C3H6
Explanation:
We can obtain the molecular formula by using the empirical formula and the molar mass in combination.
This is shown below:
[CH2]n = 42g/mol
We then add the atomic masses of carbon and hydrogen and multiply by n to give the value of n .
n[12 + 2(1)] = 42
14n = 42
n = 42/14 = 3
The molecular formula is thus [CH2]3 = C3H6
Answer:
C3H6
Explanation:
42g/mol=molar mass
14g/mol= emperical mass
42/14=3
3 times emperical
Two samples of carbon tetrachloride were decomposed into their constituent elements. One sample produced 38.9 g of carbon and 451 g of chlorine, and the other sample produced 14.8 g of carbon and 135 g of chlorine. Are these results consistent with the law of definite proportions? Show why or why not.
Answer:
No.
Explanation:
The results mentioned are not consistent with the law of definite proportions.
Law of definite proportions states that a chemical compound contains exactly the same elements in the same proportion by weight independent of its source and method of it's preparation.
In the given question, the first sample contains 38.9 g of carbon and 451 g of chlorine that means the sample has 8% of carbon and 92% of chlorine.
On the other hand, second sample contains 14.8 g of carbon and 135 g of chlorine which means that this sample has 10% of carbon and 90% of chlorine.
Since the constituent elements in both the samples are not in fixed and constant proportions (by mass), the law of definite proportions fails here.
A guitar string has a mass of 32.4 g and a length of 1.12 m. The string is pulled to a tension of 621 N. Determine the speed at which vibrations move within the string.
Answer: speed of vibration = 146.33m/s
Explanation: The speed of sound (v) in a string is related to tension (T) and mass per unit length (u) via the formula
v = √T/u
T = 621N, m =32.4g = 0.0324kg, l= 1.12m
u = mass / length, thus
u = 0.0324/ 1.12 = 0.029kg/m
Hence
v = √621/ 0.028
v = √ 21,413.793
v = 146.33m/s
Describe the differences between vitreous silica and soda-lime glass. What are some advantages and disadvantages of each of these types of glass?
Final answer:
Vitreous silica and soda-lime glass are distinct types of glass: vitreous silica has a low coefficient of expansion and excellent thermal stability, while soda-lime glass is more common, clearer, and easier to shape but has higher thermal expansion and less resistance to heat.
Explanation:
Differences Between Vitreous Silica and Soda-Lime Glass
Vitreous silica, commonly known as silica glass, and soda-lime glass are two prominent forms of glass with distinct properties and uses. Vitreous silica, which is composed predominantly of silicon dioxide (SiO2), has the valuable property of being highly transparent to both visible and ultraviolet light. The useful characteristics of vitreous silica also include a very low coefficient of expansion, which prevents it from fracturing during rapid temperature changes, making it ideal for items that undergo extreme temperature shifts, such as certain optical instruments and CorningWare.
On the other hand, soda-lime glass is a more common glass type, consisting of about 70 to 74% silica by weight mixed with sodium oxide, lime, and small amounts of other compounds such as magnesia and alumina. This type of glass is widely used for window panes, tableware, and containers, attributed to its clarity and ease of formation. Despite its widespread use, soda-lime glass does exhibit a high thermal expansion and is more prone to heat damage compared to silica glass.
Advantages and Disadvantages
Silica Glass:
Advantage: Excellent thermal stability and resistance to rapid temperature changes.
Disadvantage: More difficult to melt and shape, which may limit its use in some applications.
Soda-Lime Glass:
Advantage: Transparent and easily formed, suitable for everyday glass items.
Disadvantage: High thermal expansion and lower resistance to heat, making it less suitable for certain conditions.
In this lab we will actually mix aqueous Fe(NO3)3 with aqueous KSCN to form aqueous FeSCN2 and aqueous KNO3. a. Write the molecular form of the reaction. b. Write the complete ionic form of the reaction. c. Write the net ionic form of the reaction.
Answer :
(a) The balanced molecular equation will be,
[tex]3KSCN(aq)+Fe(NO_3)_3(aq)\rightarrow Fe(SCN)_3(aq)+3KNO_3(aq)[/tex]
(b) The complete ionic equation in separated aqueous solution will be,
[tex]3K^+(aq)+3SCN^{-}(aq)+Fe^{3+}(aq)+NO_3^{-}(aq)\rightarrow Fe^{3+}(aq)+3SCN^{-}(aq)+3K^+(aq)+3NO_3^-(aq)[/tex]
(c) In this equation the all the species are in aqueous state. So, there is no net ionic form of the reaction.
Explanation :
Complete ionic equation : In complete ionic equation, all the substance that are strong electrolyte and present in an aqueous are represented in the form of ions.
Net ionic equation : In the net ionic equations, we are not include the spectator ions in the equations.
Spectator ions : The ions present on reactant and product side which do not participate in a reactions. The same ions present on both the sides.
(a) The balanced molecular equation will be,
[tex]3KSCN(aq)+Fe(NO_3)_3(aq)\rightarrow Fe(SCN)_3(aq)+3KNO_3(aq)[/tex]
(b) The complete ionic equation in separated aqueous solution will be,
[tex]3K^+(aq)+3SCN^{-}(aq)+Fe^{3+}(aq)+NO_3^{-}(aq)\rightarrow Fe^{3+}(aq)+3SCN^{-}(aq)+3K^+(aq)+3NO_3^-(aq)[/tex]
(c) In this equation the all the species are in aqueous state. So, there is no net ionic form of the reaction.
The student's question involves the reaction between Fe(NO₃)₃ and KSCN forming FeSCN²⁺ and KNO₃. This explanation includes the molecular, complete ionic, and net ionic forms of the equation, with further context on the effect of KNO₃ on the reaction equilibrium.
Explanation:To answer the student's question, we need to write equations for the reaction between aqueous Fe(NO₃)₃ (Iron(III) nitrate) and aqueous KSCN (potassium thiocyanate) to form aqueous FeSCN²⁺ (Iron(III) thiocyanate) and aqueous KNO₃ (potassium nitrate). Here is the breakdown:
a. Molecular form of the reaction:Fe(NO₃)₃(aq) + 3 KSCN(aq) → Fe(SCN)₃(aq) + 3 KNO₃(aq)
Fe³⁺(aq) + 3 NO₃⁻(aq) + 3 K⁺(aq) + 3 SCN⁻(aq) → Fe(SCN)₃²⁺(aq) + 3 K⁺(aq) + 3 NO₃⁻(aq)
Fe³⁺(aq) + 3 SCN⁻(aq) → Fe(SCN)₃²⁺(aq)
In this experiment, the presence of Fe(SCN)²⁺ is indicated by a color change, but adding KNO₃, according to Le Chatelier's principle, will shift the equilibrium left, reducing Fe(SCN)²⁺ concentration.
If your car runs out of gas, the energy that was contained in the gas has A. been converted into chemical energy. B. created new energy. C. increased and changed form. D. been destroyed. E. been converted to several other forms of energy.
Answer:
E
Explanation:
From the law of conservation of energy, energy can neither be created nor destroyed but can be converted from one form to another. The kind of energy in fuels can be said to be chemical energy. This chemical energy in fuel is good enough to do some work by its conversion process to other forms of energy. It is the end of the last amount of this conversion that brings us to the term that the fuel is exhausted and we need to refuel so as to be able to do more work of conversion.
The chemical energy in fuels is usually converted to heat energy in cylinders which can then be converted to make the vehicle move from one point to another with a continuous conversion of this fuel.
When your car runs out of gas, the energy that was contained in the gas is converted into chemical energy.
Explanation:The correct answer is A. been converted into chemical energy.
When your car runs out of gas, the energy that was contained in the gas is not destroyed or created, but rather converted into another form of energy, specifically chemical energy. The gasoline undergoes a combustion reaction in the car's engine, releasing energy that is used to propel the vehicle.
This process can be explained by the principle of conservation of energy, which states that energy cannot be created or destroyed, only converted from one form to another.
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A sample of hydrogen gas collected over water occupied 30.0 mL at 24 °C on a day when the atmospheric pressure was 736 Torr. What volume would the hydrogen occupy if it were dry and at 0 °C and 760. Torr? The vapor pressure of water at 24 °C is 22.4 Torr
Answer:0.026ml
Explanation:
Details are found in the image attached. We must subtract the saturated vapour pressure of hydrogen gas at the given temperature from the total pressure of the hydrogen gas collected over water to obtain the actual pressure of hydrogen gas and substitute the value obtained into the general gas equation. The dry hydrogen gas has no saturated vapour pressure hence the value is substituted as given. All temperatures must be converted to Kelvin before substitution.
Aspirin, like many pharmaceutical drugs, can access the cell because it is a weak acid. This occurs because Choose one: A. it is carried by water during osmosis. B. it is a small uncharged molecule. C. it disrupts the membrane enough to squeeze through. D. as a weak acid it can cross the membrane when in its uncharged form.
Answer:
Correct answer is (D). as a weak acid it can cross the membrane when in its uncharged form.
Explanation:
Aspirin (acetylsalicylic acid, ASA) is an analgesic and anti-inflammatory agent use in the treatment of gentle to moderate pain, inflammation and fever. It is absorb in the stomach and intestine in an unchanged form.
Write and balance the equation for the formation of magnesium hydroxide and hydrogen from magnesium and water. Determine the possible mole ratios.
Final answer:
The balanced chemical equation for the formation of magnesium hydroxide and hydrogen from magnesium and water is Mg (s) + 2 H2O (l) → Mg(OH)2 (s) + H2 (g), with several possible mole ratios based on the equation's stoichiometry.
Explanation:
The equation for the formation of magnesium hydroxide and hydrogen gas from magnesium and water is:
Mg (s) + 2 H2O (l) → Mg(OH)2 (s) + H2 (g)
This reaction is balanced as written, with one atom of magnesium reacting with two molecules of water to produce one molecule of magnesium hydroxide and one molecule of hydrogen gas.
The possible mole ratios in this reaction are:
1 mole of Mg to 2 moles of H2O
1 mole of Mg to 1 mole of Mg(OH)2
1 mole of Mg to 1 mole of H2
2 moles of H2O to 1 mole of Mg(OH)2
2 moles of H2O to 1 mole of H2
These mole ratios are derived from the coefficients of each substance in the balanced chemical equation.
Burning a compound of calcium, carbon, and nitrogen in oxygen in a combustion train generates calcium oxide , carbon dioxide , nitrogen dioxide , and no other substances. A small sample gives , , and . Determine the empirical formula of the compound.
The question is incomplete, here is the complete question:
Burning a compound of calcium, carbon, and nitrogen in oxygen in a combustion train generates calcium oxide (CaO), carbon dioxide [tex](CO_2)[/tex], nitrogen dioxide [tex](NO_2)[/tex], and no other substances. A small sample gives 2.389 g CaO, 1.876 g [tex]CO_2[/tex], and 3.921 g [tex]NO_2[/tex] Determine the empirical formula of the compound.
Answer: The empirical formula for the given compound is [tex]CaCN_2[/tex]
Explanation:
The chemical equation for the combustion of compound having calcium, carbon and nitrogen follows:
[tex]Ca_xC_yN_z+O_2\rightarrow CaO+CO_2+NO_2[/tex]
where, 'x', 'y' and 'z' are the subscripts of calcium, carbon and nitrogen respectively.
We are given:
Mass of CaO = 2.389 g
Mass of [tex]CO_2=1.876g[/tex]
Mass of [tex]NO_2=3.921g[/tex]
We know that:
Molar mass of calcium oxide = 56 g/mol
Molar mass of carbon dioxide = 44 g/mol
Molar mass of nitrogen dioxide = 46 g/mol
For calculating the mass of carbon:
In 44g of carbon dioxide, 12 g of carbon is contained.
So, in 1.876 g of carbon dioxide, [tex]\frac{12}{44}\times 1.876=0.5116g[/tex] of carbon will be contained.
For calculating the mass of nitrogen:
In 46 g of nitrogen dioxide, 14 g of nitrogen is contained.
So, in 3.921 g of nitrogen dioxide, [tex]\frac{14}{46}\times 3.921=1.193g[/tex] of nitrogen will be contained.
For calculating the mass of calcium:
In 56 g of calcium oxide, 40 g of calcium is contained.
So, in 2.389 g of calcium oxide, [tex]\frac{40}{56}\times 2.389=1.706g[/tex] of calcium will be contained.
To formulate the empirical formula, we need to follow some steps:
Step 1: Converting the given masses into moles.Moles of Calcium =[tex]\frac{\text{Given mass of Calcium}}{\text{Molar mass of Calcium}}=\frac{1.706g}{40g/mole}=0.0426moles[/tex]
Moles of Carbon =[tex]\frac{\text{Given mass of Carbon}}{\text{Molar mass of Carbon}}=\frac{0.5116g}{12g/mole}=0.0426moles[/tex]
Moles of Nitrogen = [tex]\frac{\text{Given mass of Nitrogen}}{\text{Molar mass of Nitrogen}}=\frac{1.193g}{14g/mole}=0.0852moles[/tex]
Step 2: Calculating the mole ratio of the given elements.For the mole ratio, we divide each value of the moles by the smallest number of moles calculated which is 0.0426 moles.
For Calcium = [tex]\frac{0.0426}{0.0426}=1[/tex]
For Carbon = [tex]\frac{0.0426}{0.0426}=1[/tex]
For Nitrogen = [tex]\frac{0.0852}{0.0426}=2[/tex]
Step 3: Taking the mole ratio as their subscripts.The ratio of Ca : C : N = 1 : 1 : 2
Hence, the empirical formula for the given compound is [tex]CaCN_2[/tex]
The empirical formula of the compound containing calcium, carbon, and nitrogen is CaC2N.
Explanation:The empirical formula of a compound can be determined from the ratio of the elements present in the compound. In this case, we need to find the smallest whole-number ratio of calcium, carbon, and nitrogen in the compound. From the given information, we know that there is 1 calcium, 2 carbon, and 1 nitrogen in the compound. To find the empirical formula, divide each count by the smallest count, which is 1 in this case. Therefore, the empirical formula of the compound is CaC2N.
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Find the value of each of these quantities. a) C(5,1) c) C(8, 4) e) C(8, 0) b) C(5,3) d) C(8, 8) f ) C(12, 6)
The values of the given combinations are: a) 5, b) 10, c) 70, d) 1, e) 1, f) 924.
Explanation:a) C(5,1) = 5b) C(5,3) = 10c) C(8,4) = 70d) C(8,8) = 1e) C(8,0) = 1f) C(12,6) = 924Learn more about Combinations here:https://brainly.com/question/37999460
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The values of the given combinations are: a) 5, b) 10, c) 70, d) 1, e) 1, f) 924.
Explanation:a) C(5,1) = 5b) C(5,3) = 10c) C(8,4) = 70d) C(8,8) = 1e) C(8,0) = 1f) C(12,6) = 924Learn more about Combinations here:https://brainly.com/question/30646507
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When KCl dissolves in water ________. a. the K+ ions are attracted to the partial negative charge on the oxygen atom of the water molecule b. the Cl- ions are attracted to the partial negative charge on the oxygen atom of the water molecule c. the K+ ions are attracted to Cl- ions on the KCl crystal d. the K+ ions are attracted to the partial positive charge on the hydrogen atoms of the water molecule e. the Cl- ions are attracted to dissolved K+ ions
Answer:
a. the K+ ions are attracted to the partial negative charge on the oxygen atom of the water molecule.
Explanation:
The hydrogen atoms on water are partially positive and the oxygen on water is partially negative.
Since unlike charges attract, the oxygen of the water molecules are attracted to the K+ and the hydrogens are attracted to Cl-. the water surrounds the k+ and cl- so that the unlike charges are allowed to be close together.
The proper response to KCl dissolving in water is e. the Cl- ions are attracted to dissolved K+ ions.
The ionic compound KCl separates into the ions K+ and Cl- when it is introduced to water. The partial negative charges on the oxygen atoms in the water molecules are what draw the positive K+ ions to them. At the same time, the partial positive charges on the hydrogen atoms of the water molecules draw the negative Cl- ions towards them. Ion-dipole interactions are the name for this attraction between ions and water molecules.
In the case of KCl, the dissolved K+ ions in the solution selectively attract the Cl- ions. Due to the polar nature of the individual ions, the water molecules form a hydration shell around them.
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Derive an expression similar to the equation for the energy levels above for the single electron in He+ and Li2+ . Calculate the numerical values for the 1s levels (n = 1)?
Answer:
Explanation:
from Bohr's equation,
E = -Z²R/n²
R = 13.6 eV
Z = atomic number of element
for 1s energy level n= 1
E = -(Z)² x (13.6)/(1)²
E = -13.6Z²
calculating the numerical for the 1s energy levels for He+ and Li2+
- for He+
E = -13.6 * (2)² = -54.4eV
- for Li2+
E = -13.6 * (3)² = -122.4eV
A mixture of gases containing 0.20 mol of SO2 and 0.20 mol of O2 in a 4.0 L flask reacts to form SO3. If the temperature is 25ºC, what is the pressure in the flask after reaction is complete?
The pressure in the flask after the reaction is complete is approximately 1.84 atm, calculated using the Ideal Gas Law.
Explanation:This question applies the Ideal Gas Law. The balanced chemical reaction is 2SO2 + O2 → 2SO3. So, for every 2 moles of SO2, 1 mole of O2 is required and 2 moles of SO3 are produced. Given that the moles of SO2 and O2 both are 0.20 mol, all the SO2 and half of O2 will react to form 0.20 mol of SO3 leaving only 0.10 mol of O2 unreacted in the flask. Therefore, the total number of moles of gases in the flask after reaction is 0.20 mol SO3 + 0.10 mol O2 = 0.30 mol. Applying the Ideal Gas Law: Pressure (P) = nRT/V, where n = total no. of moles = 0.30 mol,R = universal gas constant = 0.0821 L·atm/(mol·K),T = temperature in Kelvin = 25ºC + 273.15 = 298.15 K, V = volume = 4.0 L. After substituting these values in the formula, we calculate the pressure to be roughly 1.84 atm.
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After reacting 0.20 mol each of SO2 and O2 to form SO3 in a 4.0 L flask at 25°C, the pressure in the flask would be 2.46 atm.
Explanation:The question presented involves the application of the Ideal Gas Law and stoichiometric relations in chemistry. Given that we have 0.20 mol of SO2 and 0.20 mol of O2 that react to form SO3, the first step is to use the balanced equation of the reaction: 2SO₂(g) + O₂(g) → 2SO₃(g). In this reaction, the total moles of gas would remain unchanged before and after the reaction. Therefore, the total number of moles of gas in the flask after the reaction would still be 0.20 + 0.20 = 0.40 mol.
Using the Ideal Gas Law PV=nRT, where P is pressure, V is volume, n is the number of moles, R is the gas constant (0.0821 L·atm/mol·K), and T is temperature in Kelvin (25°C = 298K), we can calculate the pressure. Plugging in the given values: P = nRT/V = (0.4 mol)(0.0821 L.atm/mol.K)(298 K) / 4.0 L = 2.46 atm. Thus the pressure in the flask after the reaction is complete would be 2.46 atm.
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The bcc unit cell of a substitutional alloy has atoms of element A at the corners of the unit cell and an atom of element B at the center of the unit cell. Write the formulas in terms of A and B. List element A first for both answers. 1. What is the formula of the alloy? 2. What would the formula of the alloy be if the positions of the two elements were reversed in the unit cell?
The formula of the alloy of a bcc unit cell in case of first condition is AB and if positions of atoms are interchanged then the formula is AB.
What is a unit cell?Unit cell is defined as the smallest repeating unit of crystal which when repeated leads to the generation of a crystal.They have 6 lattice parameters and seven crystal structures.Accordingly, the number of atoms in unit cells is different.
The number of atoms in each kind of unit cell is different . In case of body-centered cubic unit cell number of atoms per unit cell is 2, while those in simple cubic unit cell is one and that for face centered cubic unit cell is 4.
The concept of unit cell is used in describing the crystal structures, prediction of lattice type can be characterized by the geometry of it's unit cell.
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Final answer:
The formula of the substitutional alloy with element A at the corners and element B at the center of the BCC unit cell is AB; if the positions were reversed, the formula would remain AB because the BCC structure contains one atom from the corners and one from the center.
Explanation:
The formula of a substitutional alloy with element A at the corners and element B at the center of a body-centered cubic (BCC) unit cell is AB. In a BCC unit cell, there are eight corners, each contributing 1/8th of an atom, totaling to one atom of element A, and one full atom of element B at the center. Therefore, the formula for this alloy is AB.
If the positions of the two elements were reversed in the unit cell, with element B at the corners and element A at the center, the concept to calculate the formula remains the same. There would be one full atom of element B from the corners (8 corners*1/8th of an atom) and one full atom of element A from the center. Consequently, the formula of the alloy with reversed positions would also be AB.
Aluminum metal reacts with aqueous cobalt(II) nitrate to form aqueous aluminum nitrate and cobalt metal. What is the stoichiometric coefficient for cobalt when the chemical equation is balanced using the lowest whole-number stoichiometric coefficients?
Answer:The stoichiometric coefficient for cobalt (Co) is 1.
Explanation:
To balance the chemical equation for the reaction between aluminum metal (Al) and aqueous cobalt(II) nitrate [Co(NO3)2], you need to ensure that the number of atoms of each element is the same on both sides of the equation. The given reaction can be written as follows:
Al + Co(NO3)2 → Al(NO3)3 + Co
Now, let's balance the equation:
Balance the aluminum (Al) atoms:
There is 1 Al atom on the left and 1 Al atom on the right. Aluminum is already balanced.
Balance the cobalt (Co) atoms:
There is 1 Co atom on the left, but 1 Co atom on the right. Cobalt is already balanced.
Balance the nitrogen (N) atoms:
There are 2 nitrate ions (NO3-) on the left and 3 nitrate ions on the right (since there are three nitrate ions in Al(NO3)3). To balance the nitrogen atoms, we need to put a coefficient of 3 in front of Co(NO3)2 on the left:
Al + 3Co(NO3)2 → Al(NO3)3 + Co
Now, the nitrogen atoms are balanced.
Balance the oxygen (O) atoms:
On the left, there are 3 nitrate ions, which contribute 3 x 3 = 9 oxygen atoms. On the right, there are 3 nitrate ions and 3 oxygen atoms in Al(NO3)3, which contribute a total of 3 x 3 + 3 = 12 oxygen atoms. To balance the oxygen atoms, we need to put a coefficient of 3 in front of Al(NO3)3 on the right:
Al + 3Co(NO3)2 → 3Al(NO3)3 + Co
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An unknown compound contains only carbon, hydrogen, and oxygen (CxHyOzCxHyOz). Combustion of 5.50 gg of this compound produced 8.07 gg of carbon dioxide and 3.30 gg of water. How many moles of carbon, C, were in the original sample? Express your answer to three significant figures and include the appropriate units.
Answer:
Moles of Carbon in the product = 0.183 mol
Explanation:
Complete combustion of an organic compound in the presence of excess oxygen will give carbon dioxide (CO2) and water vapour(H2O).
Equation of reaction
CxHyOz(s) + (2x + y/2 - z)/2 O2(g) --> x CO2(g) + y/2 H2O(l)
Moles of products
CO2
Molar mass of CO2 = 12 + (16*2)
= 44 g/mol
n(CO2) = 8.07/44.0
= 0.183 mol
One compound of CO2 has 1 Carbon atom and 2 Oxygen atom.
So if we have,
0.183 moles of carbon dioxide then
0.183 moles of carbon.
The mass of carbon in the product, m = 0.183*12
= 2.20 g
H2O:
Molar mass of H2O = (1*2) + 16
= 18 g/mol
Number of moles of H2O =
= 3.3/18
= 0.183 mol
One compound of H2O has 2 Hydrogen atom and 1 Oxygen atom.
0.183 moles of water then we also have
= 2*(0.183)
= 0.367 moles of hydrogen in the sample.
The mass of hydrogen in the compound, m
= 0.367*1
= 0.367 g
Adding these two values together will give us the mass of our compound that C and H;
2.2 + 0.367
= 2.567 g
So for the Oxygen,
5.5 g - 2.567
= 2.933 g
Moles of Oxygen;
Molar mass of O = 16 g/mol
= 2.933/16
= 0.183 mol
There are 0.030 moles of carbon in the original sample as per the mole concept.
Mole is defined as the unit of amount of substance . It is the quantity measure of amount of substance of how many elementary particles are present in a given substance.
It is defined as exactly 6.022×10²³ elementary entities. The elementary entity can be a molecule, atom ion depending on the type of substance. Amount of elementary entities in a mole is called as Avogadro's number.
It is given by the formula,
[tex]\rm{number \ of \ moles}=\dfrac{\rm{mass}}{molar \ mass}[/tex]
The given values are,mass=[tex]5.50 \ g[/tex]
molar mass=[tex]178g/mol[/tex]
Substitution of values in formula gives,
[tex]\rm{number \ of \ moles}=\dfrac{5.50}{178}\\=0.030[/tex]
Thus, there are 0.030 moles of carbon in the original sample as per the mole concept.
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The density of a 0.448-m aqueous solution of K2CrO4 is 1.063 g/mL. What is the molarity (M) of this solution? The molar mass if K2CrO4 is 194.2 g/mol.
Answer:
Molarity for the solution is 0.44 mol/L
Explanation:
Let's analyse the data:
0.448 m means molality (mol of solute in 1kg of solvent)
Density = mass / volume and it always refers to solution
The molar mass of the solute, can help us to determine the mass of solute.
For molarity we need the volume of solution; remember that Molarity means the moles of solute in 1L of solution
1kg = 1000 g
Let's determine the mass of solute
0.448 mol . 194.2 g/ mol = 87 g of solute
So we have 87 g of solute and 1000 g of solvent
Mass of solution = Mass of solute + Mass of solvent
Mass of solution = 87 g + 1000 g → 1087 g
Now we can apply density for the volume
1.063 g/mL = 1087 g / Solution volume
Solution volume = 1087 g / 1.063 g/mL →1022.5 mL
Finally we must convert the volume from mL to L
1022.5 mL . 1L / 1000 mL = 1.0225 L
Molarity (mol/L) = 0.448 mol / 1.0225L → 0.44 M
An unknown compound contains only C , H , and O . Combustion of 9.30 g of this compound produced 22.7 g CO 2 and 9.29 g H 2 O . What is the empirical formula of the unknown compound? Insert subscripts as needed. empirical formula:?
Answer:
The empirical formula is = [tex]C_4H_8O[/tex]
Explanation:
Mass of water obtained = 9.29 g
Molar mass of water = 18 g/mol
Moles of [tex]H_2O[/tex] = 9.29 g /18 g/mol = 0.51611 moles
2 moles of hydrogen atoms are present in 1 mole of water. So,
Moles of H = 2 x 0.51611 = 1.03222 moles
Molar mass of H atom = 1.008 g/mol
Mass of H in molecule = 1.03222 x 1.008 = 1.0407 g
Mass of carbon dioxide obtained = 22.7 g
Molar mass of carbon dioxide = 44.01 g/mol
Moles of [tex]CO_2[/tex] = 22.7 g /44.01 g/mol = 0.5158 moles
1 mole of carbon atoms are present in 1 mole of carbon dioxide. So,
Moles of C = 0.5158 moles
Molar mass of C atom = 12.0107 g/mol
Mass of C in molecule = 0.5158 x 12.0107 = 6.1950 g
Given that the compound only contains hydrogen, oxygen and carbon. So,
Mass of O in the sample = Total mass - Mass of C - Mass of H
Mass of the sample = 9.30 g
Mass of O in sample = 9.30 - 6.1950 - 1.0407 = 2.0643 g
Molar mass of O = 15.999 g/mol
Moles of O = 2.0643 / 15.999 = 0.12903 moles
Taking the simplest ratio for H, O and C as:
1.03222 : 0.12903 : 0.5158
= 8 : 1 : 4
The empirical formula is = [tex]C_4H_8O[/tex]
A test of an automobile engine’s exhaust revealed that 3.5 g of NO2 was emitted in 10. minutes of operation. How many moles of NO2 would this engine release if it were used for a 40.-minute commute, assuming that this measured number is representative of the emission under all circumstances?
Final answer:
Given that 3.5 g of NO₂ is emitted in 10 minutes, over 40 minutes, an engine would release approximately 0.304 moles of NO₂, assuming emissions are consistent.
Explanation:
The question involves calculating the amount of NO₂ emitted from an automobile engine in moles over a specified period. Given that 3.5 g of NO₂ was emitted in 10 minutes, we can find the total amount emitted over a 40-minute period by setting up a proportion, as the emission is consistent under all circumstances. To find the number of moles, we use the molar mass of NO₂, which is approximately 46.01 g/mol.
First, calculate the total emitted mass over 40 minutes:
40 minutes / 10 minutes = 4 (since 40 minutes is four times the duration of 10 minutes)3.5 g * 4 = 14 g (total mass of NO₂ emitted over 40 minutes)Then, calculate the number of moles of NO₂:
Moles of NO₂ = Total mass of NO2 / Molar mass of NO₂Moles of NO₂ = 14 g / 46.01 g/molMoles of NO₂ ≈ 0.304 molesTherefore, if the engine were used for a 40-minute commute, it would release approximately 0.304 moles of NO₂, assuming steady emissions.
The Mendeleev and Mosley periodic charts have gaps for the as-then-undiscovered elements. Why do you think the chart used by Mosley was more accurate at predicting where new elements would be placed?
Answer:
Henry Mosley' chart was more accurate because he used 'atomic number' as the organizing principle to organize elements in its right places.Whereas Mendeleeve organized elements according to their relative atomic mass and this was giving him some problem.
Mosley's periodic chart was more accurate at predicting the placement of new elements due to its use of atomic number, whereas Mendeleev's chart was based on atomic mass.
Explanation:Mendeleev and Mosley both contributed to the development of the periodic table. However, the chart used by Mosley was more accurate at predicting the placement of new elements because Mosley's chart was based on the concept of atomic number, while Mendeleev's chart was based on atomic mass.
Atomic number is the number of protons in an atom's nucleus, while atomic mass is the total mass of protons and neutrons in an atom. Mosley's chart arranged elements in order of increasing atomic number rather than atomic mass.
This arrangement allowed for a more accurate placement of elements, as it accounted for variations in atomic mass caused by differences in the number of neutrons. As a result, Mosley's chart was able to predict the placement of new elements more accurately than Mendeleev's chart.
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Calcium carbonate is most likely to dissolve in water with which characteristics?
a. Low pressure and colder temperatures
b. Low carbon dioxide and warmer temperatures
c. Lots of carbon dioxide and warmer temperatures
d. Low pressure and warmer temperatures
e. Lots of carbon dioxide and colder temperatures
Calcium carbonate is most likely to dissolve in water with:
e. Lots of Carbon dioxide and colder temperature.
Explanation:
Calcium carbonate is very sparingly soluble in water. However, it has been observed to dissolve in cold water with higher concentration of Carbon dioxide.The reason behind the observation is the formation of Calcium bicarbonate which is soluble in water.Higher concentration of Carbon dioxide in water turns it acidic. When this acidic water reacts with calcium carbonate it forms Calcium bicarbonate which is soluble in water.So,Calcium carbonate is most likely to dissolve in water with lots of Carbon dioxide and colder temperature.Calcium carbonate is most likely to dissolve in water that has a lot of carbon dioxide and is colder, as CO2 creates acidic conditions which increase CaCO3 solubility.
Explanation:Calcium carbonate (CaCO3) is known to be more soluble in water when the conditions are acidic. The presence of carbon dioxide (CO2) in the water greatly inclines the water to be more acidic as CO2 reacts with H2O to form carbonic acid (H2CO3), which further dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-). This series of reactions results in a decrease in the concentration of carbonate ions, enabling more CaCO3 to dissolve.
Therefore, in accordance with the provided information, calcium carbonate is most likely to dissolve in water with characteristics described in option (e), which is 'lots of carbon dioxide and colder temperatures.' Colder temperatures are more favorable compared to warmer temperatures for the solubility of gas-like CO2, thereby increasing the acidity and aiding in the dissolution of CaCO3.