Q: Given the standard Gibbs free energy of formation $$\Delta G_f^\circ$$ for $$\mathrm{N_2O(g)} is$$ $$104.2\ \mathrm{kJ\ $$mol^{-1}$$} at$$ $$298.15\ \mathrm{K}$$, what is the equilibrium constant $$K$$ for its decomposition at this temperature? (Use $$R = 8.314\ \mathrm{J\ $$mol^{-1}$$\ K$$^{-1}$$})$$

$$K = \exp\left(-\frac{104200}{8.314 \times 298.15}\right)$$

Question 1

Which of the following statements best explains why the electron configuration of boron in its ground state is $$1s^2$$ $$2s^2$$ $$2p^1$$?

Accepted Answer

Because boron has five protons and five electrons, which fill the $$1s$$, $$2s$$, and one $$2p$$ orbital according to the Aufbau principle.

Question 2

A sample contains only $$^{10}B$$ and $$^{11}B$$ isotopes. If the relative atomic mass of boron is 10.81, what is the approximate percentage abundance of $$^{11}B$$?

Accepted Answer

$$81\%$$

Question 3

Which of the following molecules is expected to be linear according to the VSEPR model?

Accepted Answer

$$\mathrm{$$XeF_2$$}$$

Question 4

Which of the following best describes the resonance structures of the nitrate ion ($$\mathrm{NO_3$^-}$$)?

Accepted Answer

There are three resonance structures, each with a double bond to a different oxygen atom.

Question 5

Given the standard Gibbs free energy of formation $$\Delta G_f^\circ$$ for $$\mathrm{N_2O(g)} is$$ $$104.2\ \mathrm{kJ\ $$mol^{-1}$$} at$$ $$298.15\ \mathrm{K}$$, what is the equilibrium constant $$K$$ for its decomposition at this temperature? (Use $$R = 8.314\ \mathrm{J\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$K = \exp\left(-\frac{104200}{8.314 	imes 298.15}ight)$$

Question 6

A reaction has a rate constant $$k$$ that follows the Arrhenius equation: $$k = A \exp\left(-\frac{E_a}{RT}\right). If a $$plot of $$\ln k$$ versus $$1/T$$ yields a straight line with a slope of $$-5000\ \mathrm{K}$$, what is the activation energy $$E_a in$$ $$\mathrm{kJ\ $$mol^{-1}$$}$$? ($$R = 8.314\ \mathrm{J\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$E_a = 41.6\ \mathrm{kJ\ $$mol^{-1}$$}$$

Question 7

For a first-order reaction, the half-life $$t_{1/2} is $$given by $$t_{1/2} = \frac{\ln 2}{k}. If $$the half-life is $$19.7\ \mathrm{s}$$, what is the value of the rate constant $$k$$?

Accepted Answer

$$k = 0.0352\ \mathrm{s$$^{-1}$$}$$

Question 8

Which of the following best describes the effect of increasing temperature on the equilibrium constant $$K$$ for an endothermic reaction?

Accepted Answer

$$K$$ increases with increasing temperature.

Question 9

A buffer solution is prepared by mixing $$0.1\ \mathrm{mol} of a $$weak acid (HA) and $$0.1\ \mathrm{mol} of $$its conjugate base (A$$^-) in$$ $$1\ \mathrm{L} of $$water. If the $$pK_a of HA is$$ $$7.2$$, what is the pH of the solution?

Accepted Answer

$$7.2$$

Question 10

Which of the following is the correct expression for the solubility product constant $$K_{sp}$$ for iron(III) iodate, $$\mathrm{Fe(IO_3$)_3}$$, dissolving in water?

Accepted Answer

$$K_{sp} = [\mathrm{Fe$$^{3+}$$}][\mathrm{IO_3$^-}]^6$$

Question 11

A galvanic cell is constructed with a standard electrode potential of $$E^\circ = 0.34\ \mathrm{V}. If $$the reaction quotient $$Q = 75$$, what is the cell potential at $$25^\circ\mathrm{C}$$? ($$F = 96485\ \mathrm{C\ $$mol^{-1}$$}$$, $$R = 8.314\ \mathrm{J\ $$mol^{-1}$$\ K$$^{-1}$$})$$

Accepted Answer

$$E = 0.34\ \mathrm{V} - \frac{0.0257}{1} \ln 75$$

Question 12

Which of the following best describes the trend in first ionization energy across a period in the periodic table?

Accepted Answer

It increases from left to right.

Question 13

Which of the following is the correct balanced equation for the combustion of hydrazine ($$\mathrm{N_2H_4}) in $$oxygen, producing only nitrogen gas and water?

Accepted Answer

$$\mathrm{N_2H_4} + 2 O_2$ \rightarrow N_2$ + 2 H_2O$$

Question 14

Which of the following statements about the molecular geometry of $$\mathrm{SO_2$} is $$correct?

Accepted Answer

$$\mathrm{SO_2$} is $$bent due to one lone pair on the sulfur atom.

Question 15

Which of the following best explains why $$\mathrm{Fe(OH)_3} is $$more soluble in acidic solution than in pure water?

Accepted Answer

Because $$\mathrm{Fe(OH)_3}$$ reacts with acid to form $$\mathrm{Fe$$^{3+}$$}$$ and water, shifting the equilibrium to dissolve more solid.

Question 16

Which of the following is the correct Nernst equation for a half-cell reaction at $$25^\circ\mathrm{C}$$?

Accepted Answer

$$E = E^\circ - \frac{0.0592}{n} \log Q$$

Question 17

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

It decreases the activation energy, increasing the rate of reaction.

Question 18

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

Accepted Answer

$$K = \frac{[\mathrm{NO}]^2[\mathrm{O_2$}]}{[\mathrm{NO_2$}]^2}$$

General Chemistry Study Guide: Atomic Structure, Thermodynamics, Kinetics, Acids-Bases, Redox, and Inorganic Chemistry

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