Question 1

A sample contains 1.00 g of CO$_2$. How many oxygen atoms are present in this sample? (Molar mass of CO$_2$ = 44.0 g/mol)

Accepted Answer

$2.74 	imes 10^{22}$

Question 2

Which element has the largest atomic radius among Na, Mg, Al, and Cl?

Accepted Answer

Na

Question 3

A PES spectrum shows a peak at much higher binding energy for core electrons than valence electrons. What does this indicate about the atom?

Accepted Answer

Core electrons are more tightly bound to the nucleus.

Question 4

Which compound has the greatest lattice energy: NaCl, MgO, or CaBr$_2$? Explain.

Accepted Answer

MgO, because it has the highest charges and smallest ions.

Question 5

Which of the following best describes the energy change when ammonium nitrate dissolves in water and the temperature of the solution decreases?

Accepted Answer

The process is endothermic because heat is absorbed from the surroundings.

Question 6

A gas occupies 2.0 L at 1.0 atm and 300 K. What volume will it occupy at 1.0 atm and 450 K?

Accepted Answer

$3.0$ L

Question 7

Which of the following is the correct net ionic equation for the reaction of HCl(aq) with NaOH(aq)?

Accepted Answer

$\mathrm{H^+}(aq) + \mathrm{OH^-}(aq) \rightarrow \mathrm{H_2O}(l)$

Question 8

If a reaction releases 125 kJ of energy, what is the sign and approximate value of $\Delta H$?

Accepted Answer

$\Delta H = -125$ kJ

Question 9

Which of the following mixtures contains 1.2 g of NaCl dissolved in 50 g of water? What is the mass percent NaCl?

Accepted Answer

2.4%

Question 10

Which of the following best explains why gases deviate from ideal behavior at high pressures?

Accepted Answer

Intermolecular forces become significant.

Question 11

Which of the following is the correct formula for calculating the energy of a photon released when an electron transitions between energy levels?

Accepted Answer

$E = h 
u$

Question 12

A sealed container has a pressure of 1.2 atm at 250 K. What is the pressure at 400 K?

Accepted Answer

$1.92$ atm

Question 13

Which of the following reactions is a redox reaction?

Accepted Answer

$2\mathrm{Zn}(s) + \mathrm{O_2}(g) \rightarrow 2\mathrm{ZnO}(s)$

Question 14

Which of the following best describes the ground-state electron configuration for a neutral chromium atom?

Accepted Answer

$[Ar] 4s^1 3d^5$

Question 15

Which of the following processes is exothermic?

Accepted Answer

Combustion of methane

Question 16

Which of the following best explains why breaking strong bonds in reactants requires more energy than forming weaker bonds in products?

Accepted Answer

Bond breaking is endothermic and requires energy input.

Question 17

A solution contains two isotopes: X-35 (75.0%) and X-37 (25.0%). Calculate the average atomic mass of element X.

Accepted Answer

$35.5$ amu

Question 18

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

Accepted Answer

The reactant that is completely consumed first.

Question 19

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

Accepted Answer

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

AP Chemistry Midterm Study Guide: Atomic Structure, Bonding, Gases, Thermochemistry, and Chemical Reactions

Study Guide - Practice Questions