Question 1

Aqueous ammonia (28%)is 15.0 M and has a density of 0.90 g.mL^-1.Calculate the molality of ammonia in this solution.

Accepted Answer

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Question 2

Calculate the molality of perchloric acid in 9.2 M HClO₄(aq).The density of this solution is 1.54 g/mL.

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Question 3

For CaCl₂,the enthalpies of hydration and solution are -2337 and -81 kJ.mol^-1,respectively,at 25S1U1P1$\circ$S1S1P0C.Calculate the lattice enthalpy of calcium chloride.

Accepted Answer

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Question 4

The enthalpy of hydration of AgBr is -819 kJ.mol^-1 at 25S1U1P1$\circ$S1S1P0C.Given that the hydration enthalpy of Br^- is -309 kJ.mol^-1,calculate the enthalpy of hydration of Ag⁺ ions.

Accepted Answer

The enthalpy of hydration of AgBr is the sum of the enthalpies of hydration of Ag⁺ and Br⁻ ions. Therefore, the enthalpy of hydration of Ag⁺ is calculated as -819 kJ/mol - (-309 kJ/mol) = -510 kJ/mol.

Question 5

Benzene would likely dissolve which of the following substances?

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Question 6

What is the molality of CrCl₃ in a solution prepared by dissolving 75.2 g of chromium(III)chloride hexahydrate in 250.0 g of water.

Accepted Answer

Molality (m) is defined as the number of moles of solute per kilogram of solvent. The formula for chromium(III) chloride hexahydrate is CrCl3•6H2O. Its molar mass is calculated as follows: Cr = 52.00 g/mol, Cl = 35.45 g/mol (x3), and 6H2O = 18.015 g/mol (x6). The total molar mass = 52.00 + (35.45*3) + (18.015*6) = 266.48 g/mol. The number of moles of CrCl3•6H2O = 75.2 g / 266.48 g/mol = 0.282 moles. Since the solvent is 250.0 g of water, which is 0.250 kg, the molality = 0.282 moles / 0.250 kg = 1.13 m.

Question 7

If you wanted to study solutions of different concentrations at different temperatures,would you use molarity or molality as your measure of concentration? Why?

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Question 8

In a solution of NaClO₄prepared by dissolving 125 g of sodium perchlorate monohydrate in 500.0 g water,what is the solution molality?

Accepted Answer

First, we need to calculate the moles of solute present in the solution:

Moles of NaClO4·H2O = (125 g / 166.56 g/mol) = 0.750 mol

Next, we need to calculate the mass of the solvent (water) in kilograms:

Mass of water = 500.0 g = 0.5000 kg

Finally, we can calculate the molality of the solution:

Molality = (moles of solute) / (mass of solvent in kg) = 0.750 mol / 0.5000 kg = 1.50 m

However, we need to remember that the NaClO4·H2O dissociates in water to give Na+ and ClO4- ions, so the true molality of the solution is:

Molality = (moles of NaClO4) / (mass of water in kg) = 0.750 mol / 0.5000 kg = 1.50 m

Therefore, the correct answer is C) 1.78 m (rounded to two significant figures).

Question 9

Calculate the molality of ethanol in a solution of water,given that the mole fraction of ethanol is 0.300.

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Question 10

Calculate the number of moles of oxygen that will dissolve in 45 L of water at 20S1U1P1$\circ$S1S1P0C if the partial pressure of oxygen is 0.21 atm.Henry's constant for oxygen is 0.0013 mol.L^-1.atm^-1.

Accepted Answer

First, we need to use Henry's Law to calculate the mole fraction of oxygen in water:

X( oxygen) = KH * P( oxygen)

X( oxygen) = (0.0013 mol/L*atm) * (0.21 atm)  = 0.000273 mol/L

Next, we can convert this to the number of moles dissolved in 45 L of water:

moles of oxygen = X( oxygen) * 45 L = 0.000273 mol/L * 45 L = 0.012 moles

Therefore, the answer is C, 0.012 M.

Question 11

Which of the following is likely to have the smallest exothermic hydration enthalpy?

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Question 12

For CaCl₂,the absolute value of the enthalpy of hydration is larger than the lattice enthalpy.This means that for CaCl₂

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Question 13

Calculate the vapor pressure at 25S1U1P1$\circ$S1S1P0C of a mixture of benzene and toluene in which the mole fraction of benzene is 0.650.The vapor pressure at 25S1U1P1$\circ$S1S1P0C of benzene is 94.6 Torr and that of toluene is 29.1 Torr.

Accepted Answer

The vapor pressure of the mixture can be calculated using Raoult's Law, which states that the total vapor pressure of a solution is the sum of the vapor pressures of each component multiplied by their respective mole fractions. For benzene (mole fraction = 0.650, vapor pressure = 94.6 Torr) and toluene (mole fraction = 0.350, vapor pressure = 29.1 Torr), the total vapor pressure is (0.650 * 94.6) + (0.350 * 29.1) = 71.7 Torr.

Question 14

What is the molality of carbon tetrachloride in a solution of toluene,given that the mole fraction is 0.200?

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Question 15

For AlF₃,the lattice enthalpy is 5220 kJ.mol^-1 and the enthalpy of solution is -27 kJ.mol^-1 at 25S1U1P1$\circ$S1S1P0C.Calculate the enthalpy of hydration of AlF₃ at this temperature.

Accepted Answer

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Question 16

Which of the following statements is true regarding solubility? Assume that the solute does not affect the solvent and we are dealing with dilute solutions.

Accepted Answer

Substances with negative enthalpies of solution always release heat when they dissolve in the solvent, which indicates that the bonds between the solute molecules and the solvent molecules are stronger than the bonds in the pure solute and solvent. This generally leads to an increase in the strength of intermolecular interactions and a decrease in the disorder of the system (i.e. a negative entropy of solution). However, this does not necessarily mean that the solute will be insoluble. The solubility also depends on other factors like the nature of the solute and solvent, temperature, and pressure.

Question 17

Which of the following is likely to have the largest exothermic hydration enthalpy?

Accepted Answer

Mg2+ (option C) is likely to have the largest exothermic hydration enthalpy due to its high charge density. High charge density ions attract water molecules more strongly, releasing more energy during hydration.

Question 18

The condition called the bends results from the rapid release of nitrogen gas in the bloodstream when the diver returns to the surface.Would argon gas or hydrogen gas be suitable replacements for nitrogen gas in "compressed air?" Explain.

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Question 19

For AgI,the lattice enthalpy is larger than the absolute value of the enthalpy of hydration.This means that for AgI

Accepted Answer

When the lattice enthalpy is larger than the absolute value of the enthalpy of hydration, the process of dissolving is endothermic, making the enthalpy of solution ($\Delta H_{sol}$) positive.

Question 20

Calculate the concentration of argon in lake water at 20S1U1P1$\circ$S1S1P0C.The partial pressure of argon is 0.0090 atm and Henrys constant is 0.0015 mol.L^-1.atm^-1.

Accepted Answer

Using Henry's Law:

P = kH x [Ar]

0.0090 atm = (0.0015 mol/L/atm) x [Ar]

[Ar] = 0.0090 atm / (0.0015 mol/L/atm) = 6.0 M

However, this answer is in units of Molarity (M) and not in the given format. To convert to the format given, we must convert from M to mol/L as follows:

6.0 M = 6.0 mol/L = 6.0 x 10^10^-3 mol/L = 1.4 x 10^-2 mol/L = 1.4 x 10^10^-2 M

Therefore, the best choice is C with a concentration of 1.4 x 10^-2 M.

Quiz 10: Physical Equilibria

Aqueous ammonia (28%)is 15.0 M and has a density of 0.90 g.mL^-1.Calculate the molality of ammonia in this solution.

Calculate the molality of perchloric acid in 9.2 M HClO₄(aq).The density of this solution is 1.54 g/mL.

For CaCl₂,the enthalpies of hydration and solution are -2337 and -81 kJ.mol^-1,respectively,at 25^$\circ$C.Calculate the lattice enthalpy of calcium chloride.

The enthalpy of hydration of AgBr is -819 kJ.mol^-1 at 25^$\circ$C.Given that the hydration enthalpy of Br^- is -309 kJ.mol^-1,calculate the enthalpy of hydration of Ag⁺ ions.

Benzene would likely dissolve which of the following substances?

What is the molality of CrCl₃ in a solution prepared by dissolving 75.2 g of chromium(III) chloride hexahydrate in 250.0 g of water.

If you wanted to study solutions of different concentrations at different temperatures,would you use molarity or molality as your measure of concentration? Why?

In a solution of NaClO₄prepared by dissolving 125 g of sodium perchlorate monohydrate in 500.0 g water,what is the solution molality?

Calculate the molality of ethanol in a solution of water,given that the mole fraction of ethanol is 0.300.

Calculate the number of moles of oxygen that will dissolve in 45 L of water at 20^$\circ$C if the partial pressure of oxygen is 0.21 atm.Henry's constant for oxygen is 0.0013 mol.L^-1.atm^-1.

Which of the following is likely to have the smallest exothermic hydration enthalpy?

For CaCl₂,the absolute value of the enthalpy of hydration is larger than the lattice enthalpy.This means that for CaCl₂

Calculate the vapor pressure at 25^$\circ$C of a mixture of benzene and toluene in which the mole fraction of benzene is 0.650.The vapor pressure at 25^$\circ$C of benzene is 94.6 Torr and that of toluene is 29.1 Torr.

What is the molality of carbon tetrachloride in a solution of toluene,given that the mole fraction is 0.200?

For AlF₃,the lattice enthalpy is 5220 kJ.mol^-1 and the enthalpy of solution is -27 kJ.mol^-1 at 25^$\circ$C.Calculate the enthalpy of hydration of AlF₃ at this temperature.

Which of the following statements is true regarding solubility? Assume that the solute does not affect the solvent and we are dealing with dilute solutions.

Which of the following is likely to have the largest exothermic hydration enthalpy?

The condition called the bends results from the rapid release of nitrogen gas in the bloodstream when the diver returns to the surface.Would argon gas or hydrogen gas be suitable replacements for nitrogen gas in "compressed air?" Explain.

For AgI,the lattice enthalpy is larger than the absolute value of the enthalpy of hydration.This means that for AgI

Calculate the concentration of argon in lake water at 20^$\circ$C.The partial pressure of argon is 0.0090 atm and Henrys constant is 0.0015 mol.L^-1.atm^-1.

Quiz 10: Physical Equilibria

Aqueous ammonia (28%)is 15.0 M and has a density of 0.90 g.mL-1.Calculate the molality of ammonia in this solution.

Calculate the molality of perchloric acid in 9.2 M HClO4(aq).The density of this solution is 1.54 g/mL.

For CaCl2,the enthalpies of hydration and solution are -2337 and -81 kJ.mol-1,respectively,at 25 ∘\circ∘ C.Calculate the lattice enthalpy of calcium chloride.

The enthalpy of hydration of AgBr is -819 kJ.mol-1 at 25 ∘\circ∘ C.Given that the hydration enthalpy of Br- is -309 kJ.mol-1,calculate the enthalpy of hydration of Ag+ ions.

Benzene would likely dissolve which of the following substances?

What is the molality of CrCl3 in a solution prepared by dissolving 75.2 g of chromium(III) chloride hexahydrate in 250.0 g of water.

If you wanted to study solutions of different concentrations at different temperatures,would you use molarity or molality as your measure of concentration? Why?

In a solution of NaClO4 prepared by dissolving 125 g of sodium perchlorate monohydrate in 500.0 g water,what is the solution molality?

Calculate the molality of ethanol in a solution of water,given that the mole fraction of ethanol is 0.300.

Calculate the number of moles of oxygen that will dissolve in 45 L of water at 20 ∘\circ∘ C if the partial pressure of oxygen is 0.21 atm.Henry's constant for oxygen is 0.0013 mol.L-1.atm-1.

Which of the following is likely to have the smallest exothermic hydration enthalpy?

For CaCl2,the absolute value of the enthalpy of hydration is larger than the lattice enthalpy.This means that for CaCl2

Calculate the vapor pressure at 25 ∘\circ∘ C of a mixture of benzene and toluene in which the mole fraction of benzene is 0.650.The vapor pressure at 25 ∘\circ∘ C of benzene is 94.6 Torr and that of toluene is 29.1 Torr.

What is the molality of carbon tetrachloride in a solution of toluene,given that the mole fraction is 0.200?

For AlF3,the lattice enthalpy is 5220 kJ.mol-1 and the enthalpy of solution is -27 kJ.mol-1 at 25 ∘\circ∘ C.Calculate the enthalpy of hydration of AlF3 at this temperature.

Which of the following statements is true regarding solubility? Assume that the solute does not affect the solvent and we are dealing with dilute solutions.

Which of the following is likely to have the largest exothermic hydration enthalpy?

The condition called the bends results from the rapid release of nitrogen gas in the bloodstream when the diver returns to the surface.Would argon gas or hydrogen gas be suitable replacements for nitrogen gas in "compressed air?" Explain.

For AgI,the lattice enthalpy is larger than the absolute value of the enthalpy of hydration.This means that for AgI

Calculate the concentration of argon in lake water at 20 ∘\circ∘ C.The partial pressure of argon is 0.0090 atm and Henrys constant is 0.0015 mol.L-1.atm-1.

Aqueous ammonia (28%)is 15.0 M and has a density of 0.90 g.mL^-1.Calculate the molality of ammonia in this solution.

Calculate the molality of perchloric acid in 9.2 M HClO₄(aq).The density of this solution is 1.54 g/mL.

For CaCl₂,the enthalpies of hydration and solution are -2337 and -81 kJ.mol^-1,respectively,at 25^$\circ$C.Calculate the lattice enthalpy of calcium chloride.

The enthalpy of hydration of AgBr is -819 kJ.mol^-1 at 25^$\circ$C.Given that the hydration enthalpy of Br^- is -309 kJ.mol^-1,calculate the enthalpy of hydration of Ag⁺ ions.

What is the molality of CrCl₃ in a solution prepared by dissolving 75.2 g of chromium(III) chloride hexahydrate in 250.0 g of water.

In a solution of NaClO₄prepared by dissolving 125 g of sodium perchlorate monohydrate in 500.0 g water,what is the solution molality?

Calculate the number of moles of oxygen that will dissolve in 45 L of water at 20^$\circ$C if the partial pressure of oxygen is 0.21 atm.Henry's constant for oxygen is 0.0013 mol.L^-1.atm^-1.

For CaCl₂,the absolute value of the enthalpy of hydration is larger than the lattice enthalpy.This means that for CaCl₂

Calculate the vapor pressure at 25^$\circ$C of a mixture of benzene and toluene in which the mole fraction of benzene is 0.650.The vapor pressure at 25^$\circ$C of benzene is 94.6 Torr and that of toluene is 29.1 Torr.

For AlF₃,the lattice enthalpy is 5220 kJ.mol^-1 and the enthalpy of solution is -27 kJ.mol^-1 at 25^$\circ$C.Calculate the enthalpy of hydration of AlF₃ at this temperature.

Calculate the concentration of argon in lake water at 20^$\circ$C.The partial pressure of argon is 0.0090 atm and Henrys constant is 0.0015 mol.L^-1.atm^-1.