Q: A sample of $$CO_2$$ gas is contained in a rigid 5.00 L vessel at 25°C and 2.00 atm. How many moles of $$CO_2$$ are present? ($$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

$$n = \dfrac{PV}{RT} = \dfrac{2.00 \times 5.00}{0.0821 \times 298} = 0.41\ \mathrm{mol}$$

Q: A solution has $$[H_3O^+] = 2.5 \times 10$$^{-5}$$\ \mathrm{M}. $$What is the pH of the solution?

$$pH = -\log(2.5 \times 10$$^{-5}$$) = 4.60$$

Question 1

Which of the following statements best explains why the boiling point of water ($$H_2O) is $$much higher than that of methane ($$CH_4$$), even though both are small molecules?

Accepted Answer

Water molecules form hydrogen bonds, which are much stronger than the dispersion forces present in methane.

Question 2

A sample of $$CO_2$$ gas is contained in a rigid 5.00 L vessel at 25°C and 2.00 atm. How many moles of $$CO_2$$ are present? ($$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$n = \dfrac{PV}{RT} = \dfrac{2.00 	imes 5.00}{0.0821 	imes 298} = 0.41\ \mathrm{mol}$$

Question 3

Which of the following aqueous solutions will have the lowest freezing point? Assume all solutions are made with 1.0 mol of solute in 1.0 kg of water.

Accepted Answer

$$Na_3PO_4 ($$dissociates into 4 ions)

Question 4

A reaction has a rate law: $$	ext{rate} = k[NO_2$]^2. If $$the concentration of $$NO_2 is $$doubled, what happens to the rate?

Accepted Answer

The rate increases by a factor of 4.

Question 5

Consider the equilibrium: $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$. If the volume of the reaction vessel is decreased at constant temperature, what will happen to the amount of NH_3$ at equilibrium?

Accepted Answer

The amount of $$NH_3$$ will increase.

Question 6

Which of the following is a correct Lewis structure for the nitrate ion, $$NO_3$$^-$$?

Accepted Answer

A structure with three resonance forms, each with one double bond to an oxygen and two single bonds, with a negative charge delocalized over the three oxygens.

Question 7

Which of the following statements about buffers is TRUE?

Accepted Answer

A buffer is most effective when $$[HA] \approx [A^-]$$ and $$pH \approx pK_a.$$

Question 8

Which of the following is the correct expression for the solubility product constant ($$K_{sp}) $$for $$CaF_2$$?

Accepted Answer

$$K_{sp} = [Ca$$^{2+}$$][F^-]^2$$

Question 9

A solution has $$[H_3O^+] = 2.5 	imes 10$$^{-5}$$\ \mathrm{M}. $$What is the pH of the solution?

Accepted Answer

$$pH = -\log(2.5 	imes 10$$^{-5}$$) = 4.60$$

Question 10

Which of the following statements about entropy ($$S) is $$correct?

Accepted Answer

For a spontaneous process, the total entropy of the universe increases ($$\Delta S_{univ} \u003e 0).$$

Question 11

Which of the following is the correct relationship between the standard free energy change and the equilibrium constant?

Accepted Answer

$$\Delta G^\circ = -RT \ln K$$

Question 12

Which of the following is the correct cell notation for a galvanic cell based on the reaction: $$Zn(s) + Cu$$^{2+}$$(aq) \rightarrow Zn$$^{2+}$$(aq) + Cu(s)$$?

Accepted Answer

$$Zn(s) | Zn$$^{2+}$$(aq) || Cu$$^{2+}$$(aq) | Cu(s)$$

Question 13

A radioactive isotope decays with a half-life of 10 years. If you start with 80 g, how much remains after 30 years?

Accepted Answer

$$10\ \mathrm{g}$$

Question 14

Which of the following is a correct statement about the quantum numbers for an electron in an atom?

Accepted Answer

The magnetic quantum number $$m_l$$ can have integer values from $$-l to$$ $$+l.$$

Question 15

Which of the following compounds is a strong acid?

Accepted Answer

$$HNO_3$$

Question 16

Which of the following best describes the effect of adding $$NaCl to a $$saturated solution of $$AgCl$$?

Accepted Answer

The solubility of $$AgCl$$ decreases due to the common ion effect.

Question 17

Which of the following is the correct formula for calculating the density of a substance?

Accepted Answer

$$d = \dfrac{m}{V}$$

Question 18

Which of the following statements about metals is TRUE?

Accepted Answer

Metals tend to lose electrons and form cations.

Question 19

Which of the following is the correct formula for the energy of a photon?

Accepted Answer

$$E = h
u = \dfrac{hc}{\lambda}$$

Comprehensive General Chemistry Study Guide: Final Exam Review

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