Question 1

Which of the following will have the largest lattice energy?

Accepted Answer

NaF has the largest lattice energy because lattice energy increases with the charge of the ions and decreases as the size of the ions increases. NaF has the smallest ions among the options, leading to stronger electrostatic attraction and thus higher lattice energy.

Question 2

Indicate which aqueous solution has the fastest evaporation rate.

Accepted Answer

A

Question 3

The vapor pressure of an aqueous solution is found to be 24.9 mm Hg at 25°C. What is the mole fraction of solute in this solution? The vapor pressure of water is 25.756 mm Hg at 25°C.

Accepted Answer

The mole fraction (X) of solute can be calculated using Raoult's law:

Ptotal = Pwater * Xwater + Psolute * Xsolute

where Ptotal is the total vapor pressure of the solution, Pwater is the vapor pressure of pure water, and Psolute is the vapor pressure of the solute (which is negligible in this case).

Solving for Xsolute:

Xsolute = (Ptotal - Pwater * Xwater) / Psolute

Plugging in the values given:

Xsolute = (24.9 mm Hg - 25.756 mm Hg * Xwater) / Psolute

We need to find Xwater first. Since this is an aqueous solution, we can assume that the solvent is water and therefore the mole fraction of water is 1 - Xsolute.

To find Xwater, we can use the fact that the mole fractions of solute and solvent add up to 1:

Xwater = 1 - Xsolute

Substituting this into the equation above and rearranging:

Xsolute = (Pwater - Ptotal) / (Pwater - Psolute)

Xsolute = (25.756 mm Hg - 24.9 mm Hg) / (25.756 mm Hg - 0 mm Hg)

Xsolute = 0.03323

Therefore, the mole fraction of solute in this solution is 0.0332, which is choice B.

Question 4

Which of the following is needed to calculate the lattice energy of an ionic compound?

Accepted Answer

Ionization energy is directly related to the process of forming an ionic compound, as it measures the energy required to remove an electron from an atom or ion, a key step in the formation of cations, which then combine with anions to form ionic compounds.

Question 5

Calculate the lattice energy of sodium fluoride from the following data: Ionization energy of Na: 496 kJ/mol Electron affinity of F: -328 kJ/mol Energy to vaporize Na: 108 kJ/mol F₂ bond energy: 160 kJ/mol Energy change for the reaction: Na(s) +F₂(g) $\rightarrow$NaF(s); $\Delta$H = -575 kJ

Accepted Answer

The answer of Calculate the lattice energy of sodium fluoride...

Question 6

Indicate which aqueous solution has the slowest evaporation rate.

Accepted Answer

The compound in choice B, Na₂CO₃, is a complex sulfonate that has a high molecular weight and high number of ions in solution. These factors lead to a decrease in the evaporation rate of the solution, making it the slowest evaporating option.

Question 7

Which of the solutions shown here will have the highest vapor pressure? White circles indicate solvent molecules; black circles indicate molecules of a nonvolatile solute.

Accepted Answer

The solution with the highest vapor pressure will have the most solvent molecules at the surface, as those are the ones most likely to evaporate. In solution A, there are only solvent molecules present at the surface, while solutions B, C, and D also have nonvolatile solute molecules present. Therefore, solution A will have the highest vapor pressure.

Question 8

Determine the energy change for the reaction Li(s) + Cl₂(g) $\rightarrow$LiCl(s) From the following data: Lattice energy of LiCl = -861 kJ/mol Energy to vaporize Li = 159 kJ/mol Ionization energy of Li = 520 kJ/mol Cl₂ bond energy: 240 kJ/mol Electron affinity of Cl: -349 kJ/mol

Accepted Answer

The answer of Determine the energy change for the reaction...

Question 9

At 25°C, the vapor pressure of pure water is 25.756 mm Hg. What is the vapor pressure of water in a 0.500 m solution of sodium chloride?

Accepted Answer

The answer of At 25°C, the vapor pressure of pure...

Question 10

Which listing of ionic compounds is in order of increasing melting point?

Accepted Answer

The answer of Which listing of ionic compounds is in...

Question 11

Which of the solutions shown here will have the lowest vapor pressure? White circles indicate solvent molecules; black circles indicate molecules of a nonvolatile solute.

Accepted Answer

The solution with the lowest vapor pressure is the one with the highest concentration of nonvolatile solute. In this case, solution D has the most nonvolatile solute molecules, as indicated by the larger number of black circles. The presence of nonvolatile solute molecules reduces the number of solvent molecules at the surface and thus reduces the tendency for the solvent to evaporate.

Question 12

Which of the following is not typically needed to calculate the lattice energy of an ionic compound?

Accepted Answer

The answer of Which of the following is not typically...

Question 13

Indicate which aqueous solution has the lowest vapor pressure.

Accepted Answer

The vapor pressure of a solution is primarily determined by the concentration of solute particles in the solution because solute particles lower the vapor pressure by inhibiting the escape of solvent molecules into the gas phase. Among the given options, 0.2 M MgCl₂ will dissociate into three ions (1 Mg²⁺ and 2 Cl⁻) per formula unit, resulting in the highest number of particles in solution. Since option E has the highest concentration of a solute that dissociates into multiple particles, it will have the lowest vapor pressure due to the highest decrease in vapor pressure relative to the pure solvent.

Question 14

Indicate which aqueous solution has the highest vapor pressure.

Accepted Answer

Vapor pressure of a solution is inversely related to the concentration of solute particles in the solution. 0.1 M KCl has the lowest concentration of solute particles among the options, leading to the highest vapor pressure.

Question 15

Which of the following compounds has the largest melting point?

Accepted Answer

Beryllium fluoride sulfide (BeF₂) has the largest melting point among the given compounds because it is a covalent compound with highly polar bonds due to the large electronegativity difference between beryllium and fluorine. The presence of sulfur in the compound also contributes to its high melting point due to the strong bonds between sulfur and the surrounding atoms. In contrast, the other compounds are all ionic and have smaller electronegativity differences, leading to weaker bonds and lower melting points.

Question 16

Which of the following requires the smallest energy to separate the ions?

Accepted Answer

The answer of Which of the following requires the smallest...

Question 17

Which of the following ranks the compounds from lowest to highest lattice energy?

Accepted Answer

The answer of Which of the following ranks the compounds...

Question 18

Coulomb's law states that the interaction energy between ions depends __________

Accepted Answer

Coulomb's law states that the interaction energy between ions depends directly on the ionic charges and inversely on the distance between the ions.

Question 19

What is the vapor pressure of an aqueous solution that has a solute mol fraction of $\chi$ = 0.100? The vapor pressure of water is 25.756 mm Hg at 25°C.

Accepted Answer

The answer of What is the vapor pressure of an...

Question 20

Which of the following will require the greatest energy input to separate the ions?

Accepted Answer

The answer of Which of the following will require the...

Quiz 11: Solutions and Their Colligative Properties