Q: A sample of gas occupies 2.50 L at 1.00 atm and 298 K. If the pressure is increased to 2.00 atm and the temperature is decreased to 273 K, what will be the new volume of the gas? (Assume ideal gas behavior.)

$V_2 = V_1 \times \frac{P_1}{P_2} \times \frac{T_2}{T_1} = 2.50 \times \frac{1.00}{2.00} \times \frac{273}{298} = 1.14\ \mathrm{L}$

Q: A 5.00 g sample of an unknown gas occupies 10.0 L at 300 K and 1.00 atm. What is the molar mass of the gas? (Use $R = 0.0821\ \mathrm{L\cdot atm\cdot mol^{-1}\cdot K^{-1}}$)

$M = \frac{mRT}{PV} = \frac{5.00 \times 0.0821 \times 300}{1.00 \times 10.0} = 12.3\ \mathrm{g/mol}$

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

$\text{Density} = \frac{\text{mass}}{\text{volume}}$

Question 1

A sample of gas occupies 2.50 L at 1.00 atm and 298 K. If the pressure is increased to 2.00 atm and the temperature is decreased to 273 K, what will be the new volume of the gas? (Assume ideal gas behavior.)

Accepted Answer

$V_2 = V_1 	imes \frac{P_1}{P_2} 	imes \frac{T_2}{T_1} = 2.50 	imes \frac{1.00}{2.00} 	imes \frac{273}{298} = 1.14\ \mathrm{L}$

Question 2

Which of the following statements best explains why the atomic radius increases as you move down a group in the periodic table?

Accepted Answer

The number of energy levels increases, causing the outer electrons to be farther from the nucleus.

Question 3

A 5.00 g sample of an unknown gas occupies 10.0 L at 300 K and 1.00 atm. What is the molar mass of the gas? (Use $R = 0.0821\ \mathrm{L\cdot atm\cdot mol^{-1}\cdot K^{-1}}$)

Accepted Answer

$M = \frac{mRT}{PV} = \frac{5.00 	imes 0.0821 	imes 300}{1.00 	imes 10.0} = 12.3\ \mathrm{g/mol}$

Question 4

Which of the following is the correct electron configuration for a ground-state sulfur atom ($Z=16$)?

Accepted Answer

$1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^4$

Question 5

Which of the following best describes the trend in ionization energy across a period from left to right?

Accepted Answer

Ionization energy increases due to increasing effective nuclear charge.

Question 6

A reaction has $\Delta H = -125\ \mathrm{kJ}$ and $\Delta S = -200\ \mathrm{J/K}$. At what temperature (in K) does the reaction change from spontaneous to nonspontaneous?

Accepted Answer

$T = \frac{\Delta H}{\Delta S} = \frac{-125,000}{-200} = 625\ \mathrm{K}$

Question 7

Which of the following is the correct balanced equation for the combustion of propane ($C_3H_8$)?

Accepted Answer

$C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O$

Question 8

A solution is prepared by dissolving 0.50 mol of NaCl in enough water to make 1.0 L of solution. What is the molarity of the solution?

Accepted Answer

$M = \frac{0.50\ \mathrm{mol}}{1.0\ \mathrm{L}} = 0.50\ \mathrm{M}$

Question 9

Which of the following elements has the highest electronegativity?

Accepted Answer

Fluorine

Question 10

A 10.0 g sample of ice at $0\ ^\circ\mathrm{C}$ is added to 100.0 g of water at $30.0\ ^\circ\mathrm{C}$. What is the final temperature of the mixture? ($\Delta H_{fus} = 334\ \mathrm{J/g}$, $c_{water} = 4.18\ \mathrm{J/g\cdot ^\circ C}$)

Accepted Answer

The final temperature is $17.0\ ^\circ\mathrm{C}$.

Question 11

Which of the following best describes the difference between a covalent bond and an ionic bond?

Accepted Answer

A covalent bond involves the sharing of electrons, while an ionic bond involves the transfer of electrons.

Question 12

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

Accepted Answer

$	ext{Density} = \frac{	ext{mass}}{	ext{volume}}$

Question 13

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

Accepted Answer

$E = h
u$

Question 14

A sample of nitrogen gas is collected over water at $25\ ^\circ\mathrm{C}$ and 760 mm Hg. The vapor pressure of water at $25\ ^\circ\mathrm{C}$ is 24 mm Hg. What is the partial pressure of the nitrogen gas?

Accepted Answer

$P_{N_2} = 760\ \mathrm{mm\ Hg} - 24\ \mathrm{mm\ Hg} = 736\ \mathrm{mm\ Hg}$

Question 15

Which of the following is the correct relationship for the speed of light?

Accepted Answer

$c = \lambda 
u$

Question 16

Which of the following is the correct formula for calculating the percent composition by mass of an element in a compound?

Accepted Answer

$\%\ 	ext{composition} = \frac{	ext{mass of element}}{	ext{molar mass of compound}} 	imes 100$

Question 17

Which of the following is the correct formula for the ideal gas law?

Accepted Answer

$PV = nRT$

Question 18

Which of the following is the correct formula for calculating the heat absorbed or released by a substance?

Accepted Answer

$q = mc\Delta T$

Question 19

Which of the following is the correct formula for calculating the change in enthalpy for a reaction?

Accepted Answer

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

General Chemistry Reference Sheet: Constants, Equations, and the Periodic Table

Study Guide - Practice Questions

Study Guide - Flashcards