Question 1

A sample of nitrogen gas is collected at 1.78 atm and 30\degree C in a tube with a volume of 4.80 g. What is the volume of the gas? (Molar mass of N$$_2 = 28.0 g/$$mol; $$R = 0.08206 L$$·atm·mol$$^{-1}$$·K$$^{-1})$$

Accepted Answer

$$6.62 L$$

Question 2

Given the reaction: $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$ with $$\Delta H = -92.4$$ kJ, what will happen to the equilibrium if the temperature is increased?

Accepted Answer

The equilibrium will shift to the left, producing more $$N_2$$ and $$H_2.$$

Question 3

A compound $$XCl_2$$ contains 75.0\% Cl by mass. What is the element X? (Atomic masses: Cl = 35.5, Mg = 24.3, Ca = 40.1, Fe = 55.8)

Accepted Answer

Mg

Question 4

Which of the following is NOT a property of enthalpy as a thermodynamic function?

Accepted Answer

It depends on the path taken.

Question 5

A snack food contains 12\% protein, 14\% fat, and 54\% carbohydrate by mass. If proteins and carbohydrates provide 4 Cal/g and fats provide 9 Cal/g, what percentage of the total calories comes from fat?

Accepted Answer

41\%

Question 6

Which of the following best describes Le Châtelier’s Principle?

Accepted Answer

A system at equilibrium will shift to minimize the effect of a disturbance.

Question 7

Given $$\Delta G^\circ = -53.22 kJ/$$mol for $$H_2(g$$) + $$Br_2(g$$) \rightarrow 2HBr(g)$$ at 298 K, calculate K$$_{eq}$$ for the reaction. (R = 8.314$ J/mol·K)

Accepted Answer

$$K_{eq} = 1.2 	imes 10^9$

Question 8

Which of the following statements about the autoionization of water is correct?

Accepted Answer

The equilibrium constant $$K_w$$ increases with increasing temperature.

Question 9

A buffer solution is prepared by mixing 0.10 mol of acetic acid ($$K_a = 1.8 	imes 10$$^{-5}$$) and 0.10 mol of sodium acetate in 1.0 L of water. What is the pH of the buffer?

Accepted Answer

$$4.74$$

Question 10

Which of the following best describes the limiting reagent in a chemical reaction?

Accepted Answer

The reactant that is completely consumed first, limiting the amount of product formed.

Question 11

Which of the following is the correct balanced equation for the reduction of permanganate ion ($$MnO_4$$^-$$) by chloride ion (Cl$$^-$$) in basic solution?

Accepted Answer

$$2MnO_4^- + 3Cl^- + 4H_2O \rightarrow 2MnO_2 + 3ClO_2^- + 8OH^-$$

Question 12

A 0.0200 M solution of HCl has a pH of:

Accepted Answer

$$1.70$$

Question 13

Which of the following changes will increase the solubility of Zn(OH)$$_2 in a $$buffer solution with pH = 11.4?

Accepted Answer

Decreasing the pH of the solution.

Question 14

If a single cylinder of an automobile engine has a volume of 524 cm$$^3$$ and is filled with dry air at 25$$^\circC $$and 900 mm Hg, how many moles of O$$_2$$ are present? (Mole fraction of O$$_2 in $$dry air = 0.2095; $$R = 0.08206 L$$·atm·mol$$^{-1}$$·K$$^{-1})$$

Accepted Answer

$$0.0081$$ mol

Question 15

Which of the following best explains why the equilibrium constant $$K_{eq}$$ changes with temperature?

Accepted Answer

Because $$\Delta G^\circ is $$temperature dependent.

Question 16

Which of the following is the correct expression for the equilibrium constant $$K_c$$ for the reaction $$2NO_2(g) \rightleftharpoons 2NO(g) + O_2$(g)$$?

Accepted Answer

$$K_c = \dfrac{[NO]^2[O_2$]}{[NO_2$]^2}$$

Question 17

Which of the following is the correct formula for calculating the standard Gibbs free energy change ($$\Delta G^\circ) $$for a reaction?

Accepted Answer

$$\Delta G^\circ = \Delta H^\circ - T\Delta S^\circ$$

Question 18

Which of the following best describes the effect of adding NaOH to a buffer solution containing acetic acid and sodium acetate?

Accepted Answer

The pH increases slightly.

Question 19

Which of the following is the correct relationship between $$K_a$$, $$K_b$$, and $$K_w$$ for a conjugate acid-base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

General Chemistry 101: Final Exam Study Guide

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