Question 1

Which of the following best describes a precipitation reaction?

Accepted Answer

A reaction in which an insoluble solid forms when two solutions are mixed.

Question 2

Which equation correctly represents the neutralization of hydrochloric acid with sodium hydroxide?

Accepted Answer

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

Question 3

A student mixes solutions of silver nitrate and sodium chloride. What is the precipitate formed?

Accepted Answer

$$\mathrm{AgCl}$$

Question 4

Which of the following is the correct balanced equation for the combustion of methane?

Accepted Answer

$$\mathrm{CH_4$} + 2\mathrm{O_2$} \rightarrow \mathrm{CO_2$} + 2\mathrm{H_2O}$$

Question 5

If 2.00 mol of $$\mathrm{H_2$}$$ reacts with 1.00 mol of $$\mathrm{O_2$} to $$form water, what is the limiting reactant?

Accepted Answer

$$\mathrm{O_2$}$$

Question 6

Calculate the enthalpy change ($$\Delta H) $$for a reaction that absorbs 150 kJ of heat from the surroundings.

Accepted Answer

$$\Delta H = +150\ \mathrm{kJ}$$

Question 7

Which of the following phase changes is exothermic?

Accepted Answer

Condensation

Question 8

A reaction releases 250 J of heat and does 100 J of work on the surroundings. What is the change in internal energy ($$\Delta U$$)?

Accepted Answer

$$\Delta U = -150\ \mathrm{J}$$

Question 9

Which of the following best describes Hess's Law?

Accepted Answer

The enthalpy change for a reaction is the same, regardless of the number of steps in the reaction.

Question 10

Which of the following equations represents the heat required to change the temperature of a substance?

Accepted Answer

$$q = m c \Delta T$$

Question 11

A sample of ice at $$0^\circC is $$heated until it becomes steam at $$100^\circC. $$Which of the following steps requires the most energy per gram?

Accepted Answer

Vaporizing the water at $$100^\circC$$

Question 12

Which of the following is a gas-evolution reaction?

Accepted Answer

$$\mathrm{Na_2CO_3} (aq) + 2\mathrm{HCl} (aq) \rightarrow 2\mathrm{NaCl} (aq) + \mathrm{H_2O} (l) + \mathrm{CO_2$} (g)$$

Question 13

A reaction has $$\Delta H = -200\ \mathrm{kJ}. $$Which statement is true?

Accepted Answer

The reaction is exothermic and releases heat.

Question 14

Which of the following best describes the process of sublimation?

Accepted Answer

A solid changing directly to a gas.

Question 15

If 0.50 mol of $$\mathrm{$$CaCl_2$$} is $$dissolved in water, how many moles of chloride ions are produced?

Accepted Answer

1.0 mol

Question 16

Which of the following statements about enthalpy is correct?

Accepted Answer

Enthalpy is a state function and depends only on the initial and final states.

Question 17

A 10.0 g sample of water is heated from $$25^\circC to$$ $$75^\circC. If $$the specific heat of water is $$4.18\ \mathrm{J/g\cdot ^\circ C}$$, how much heat is absorbed?

Accepted Answer

$$2090\ \mathrm{J}$$

Question 18

Which of the following is true about the stoichiometry of the reaction $$2\mathrm{H_2$} + \mathrm{O_2$} \rightarrow 2\mathrm{H_2O}$$?

Accepted Answer

2 moles of $$\mathrm{H_2$}$$ react with 1 mole of $$\mathrm{O_2$} to $$produce 2 moles of $$\mathrm{H_2O}.$$

Question 19

Which of the following best explains why ice floats on water?

Accepted Answer

Ice is less dense than liquid water due to its molecular structure.

Question 20

A chemical reaction occurs in a closed container at constant pressure and releases 500 J of heat. What is the value of $$\Delta H$$?

Accepted Answer

$$\Delta H = -500\ \mathrm{J}$$

Exam 3 Study Guide: Precipitation, Stoichiometry, Thermochemistry, Phase Changes, and Reaction Enthalpy

Study Guide - Practice Questions

Study Guide - Flashcards