Question 1

Which of the following best explains why carbon dioxide ($$\mathrm{CO_2$}) is a $$greenhouse gas, but nitrogen ($$\mathrm{N_2$}) $$and oxygen ($$\mathrm{O_2$}) $$are not?

Accepted Answer

Because $$\mathrm{CO_2$}$$ has vibrational modes that are IR-active due to symmetry breaking, while $$\mathrm{N_2$}$$ and $$\mathrm{O_2$} do $$not.

Question 2

A student is given 10.0 g of propane ($$\mathrm{C_3H_8}) $$and 40.0 g of oxygen ($$\mathrm{O_2$}) to $$combust completely. The balanced equation is:

$$\mathrm{C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(l)}$$

Which reactant is the limiting reactant?

Accepted Answer

$$\mathrm{C_3H_8}$$

Question 3

Which of the following statements about Beer's Law is correct?

Accepted Answer

According to Beer's Law, $$A = \varepsilon b c$$, where $$A is $$absorbance, $$\varepsilon is $$the molar absorptivity, $$b is $$the path length, and $$c is $$the concentration.

Question 4

A solution is prepared by dissolving 0.50 mol of NaCl in enough water to make 2.0 L of solution. What is the molarity of the solution?

Accepted Answer

$$0.25\ \mathrm{M}$$

Question 5

Which of the following best describes a precipitation reaction?

Accepted Answer

A reaction in which two aqueous ionic solutions combine to form an insoluble solid.

Question 6

Which of the following is the correct net ionic equation for the reaction between aqueous solutions of silver nitrate and sodium chloride?

Accepted Answer

$$\mathrm{Ag^+(aq) + Cl^-(aq) \rightarrow AgCl(s)}$$

Question 7

A 25.0 mL sample of 0.100 M HCl is titrated with 0.200 M NaOH. What volume of NaOH is required to reach the equivalence point?

$$\mathrm{HCl(aq) + NaOH(aq) \rightarrow NaCl(aq) + H_2O(l)}$$

Accepted Answer

$$12.5\ \mathrm{mL}$$

Question 8

Which of the following is a correct statement about strong electrolytes?

Accepted Answer

Strong electrolytes dissociate completely into ions in aqueous solution.

Question 9

Which of the following is the correct definition of an Arrhenius acid?

Accepted Answer

A substance that increases the concentration of $$\mathrm{H^+}$$ ions in aqueous solution.

Question 10

Which of the following compounds is insoluble in water according to the abbreviated solubility rules provided?

Accepted Answer

$$\mathrm{$$CaCO_3$$}$$

Question 11

A reaction has a $$\Delta H of$$ $$-250\ \mathrm{kJ}. $$Which of the following statements is true?

Accepted Answer

The reaction is exothermic and releases heat to the surroundings.

Question 12

Which of the following is a state function?

Accepted Answer

Enthalpy ($$\Delta H)$$

Question 13

Given the following reactions and their enthalpies:

$$\mathrm{C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(l)}\ \Delta H = -2219\ \mathrm{kJ}$$

$$\mathrm{C_3H_8(g) \rightarrow 3C(s) + 4H_2(g)}\ \Delta H = +104\ \mathrm{kJ}$$

$$\mathrm{C(s) + O_2$(g) \rightarrow CO_2$(g)}\ \Delta H = -394\ \mathrm{kJ}$$

$$\mathrm{H_2$(g) + 1/2O_2(g) \rightarrow H_2O(l)}\ \Delta H = -286\ \mathrm{kJ}$$

What is the enthalpy of formation ($$\Delta H_f) of $$propane ($$\mathrm{C_3H_8(g)}$$)?

Accepted Answer

$$-104\ \mathrm{kJ\ $$mol^{-1}$$}$$

Question 14

Which of the following best describes the sign conventions for $$q$$ and $$w in $$the First Law of Thermodynamics ($$\Delta E = q + w$$)?

Accepted Answer

$$q is $$positive when heat is absorbed by the system; $$w is $$positive when work is done on the system.

Question 15

A 100.0 g sample of water is heated from $$25.0^\circ\mathrm{C} to$$ $$75.0^\circ\mathrm{C}. $$The specific heat of water is $$4.18\ \mathrm{J\ g$$^{-1}$$\ ^\circ C$$^{-1}$$}. $$How much heat is absorbed by the water?

Accepted Answer

$$20,900\ \mathrm{J}$$

Question 16

Which of the following is the correct expression for the enthalpy change of a reaction using standard heats of formation?

Accepted Answer

$$\Delta H = \sum n \Delta H_{f,\mathrm{products}} - \sum n \Delta H_{f,\mathrm{reactants}}$$

Question 17

Which of the following is a correct example of a formation reaction?

Accepted Answer

$$\mathrm{C(s) + O_2$(g) \rightarrow CO_2$(g)}$$

Question 18

Which of the following statements about water is correct and helps explain its central role in biological and environmental systems?

Accepted Answer

Water has a high heat capacity, allowing it to moderate temperature changes in organisms and environments.

Question 19

Which of the following best describes the process of resonance in energy transfer, as demonstrated by pushing a swing?

Accepted Answer

Resonance occurs when the frequency of the applied force matches the natural frequency of the system, resulting in efficient energy transfer.

Question 20

Which of the following best describes the role of a reducing agent in a redox reaction?

Accepted Answer

The reducing agent donates electrons and is itself oxidized.

Chemistry 1770 Exam #3 Study Guide: Stoichiometry, Solution Chemistry, and Energy

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