Q: A sample of gas occupies 2.50 L at 1.00 atm and 300 K. If the pressure is increased to 2.00 atm and the temperature is decreased to 150 K, what is the new volume of the gas? (Assume ideal gas behavior.)

$V_2 = V_1 \times \frac{P_1}{P_2} \times \frac{T_2}{T_1} = 2.50\,\mathrm{L} \times \frac{1.00}{2.00} \times \frac{150}{300} = 0.625\,\mathrm{L}$

Question 1

Which of the following best explains why ionic compounds generally have higher melting points than covalent compounds?

Accepted Answer

Ionic compounds have stronger electrostatic forces between ions, requiring more energy to separate them.

Question 2

A sample of gas occupies 2.50 L at 1.00 atm and 300 K. If the pressure is increased to 2.00 atm and the temperature is decreased to 150 K, what is the new volume of the gas? (Assume ideal gas behavior.)

Accepted Answer

$V_2 = V_1 	imes \frac{P_1}{P_2} 	imes \frac{T_2}{T_1} = 2.50\,\mathrm{L} 	imes \frac{1.00}{2.00} 	imes \frac{150}{300} = 0.625\,\mathrm{L}$

Question 3

Which of the following statements about the periodic trends in atomic radius is correct?

Accepted Answer

Atomic radius decreases across a period from left to right due to increasing effective nuclear charge.

Question 4

Which of the following best describes the difference between a sigma ($\sigma$) bond and a pi ($\pi$) bond?

Accepted Answer

A $\sigma$ bond results from head-on overlap of orbitals, while a $\pi$ bond results from side-to-side overlap.

Question 5

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

Accepted Answer

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

Question 6

Which of the following molecules is nonpolar, despite having polar bonds?

Accepted Answer

$\mathrm{CO}_2$

Question 7

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

A catalyst lowers the activation energy, increasing the reaction rate without being consumed.

Question 8

Which of the following is the correct electron configuration for a ground-state phosphorus atom ($Z=15$)?

Accepted Answer

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

Question 9

Which of the following statements about intermolecular forces is correct?

Accepted Answer

Hydrogen bonding is a special case of dipole-dipole interaction that occurs when hydrogen is bonded to N, O, or F.

Question 10

A 0.500 mol sample of $\mathrm{NaCl}$ is dissolved in enough water to make 1.00 L of solution. What is the molarity of the solution?

Accepted Answer

$0.500\ \mathrm{M}$

Question 11

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

Accepted Answer

Ice is less dense than liquid water due to the open hexagonal structure formed by hydrogen bonding.

Question 12

Which of the following is the correct balanced equation for the combustion of propane ($\mathrm{C}_3\mathrm{H}_8$)?

Accepted Answer

$\mathrm{C}_3\mathrm{H}_8 + 5\ \mathrm{O}_2 \rightarrow 3\ \mathrm{CO}_2 + 4\ \mathrm{H}_2\mathrm{O}$

Question 13

Which of the following best describes the effect of increasing temperature on the rate of a chemical reaction?

Accepted Answer

Increasing temperature increases the kinetic energy of molecules, leading to more frequent and energetic collisions.

Question 14

Which of the following is the correct expression for the equilibrium constant $K_c$ for the reaction $2\ \mathrm{NO}_2(g) \rightleftharpoons \mathrm{N}_2\mathrm{O}_4(g)$?

Accepted Answer

$K_c = \frac{[\mathrm{N}_2\mathrm{O}_4]}{[\mathrm{NO}_2]^2}$

Question 15

Which of the following statements about the first law of thermodynamics is correct?

Accepted Answer

The first law states that energy cannot be created or destroyed, only transformed.

Question 16

Which of the following best describes the hybridization of the central atom in methane ($\mathrm{CH}_4$)?

Accepted Answer

$sp^3$

Question 17

Which of the following is a correct statement about the relationship between molecular structure and boiling point?

Accepted Answer

Molecules with stronger intermolecular forces generally have higher boiling points.

Question 18

Which of the following is the correct Lewis structure for carbon dioxide ($\mathrm{CO}_2$)?

Accepted Answer

O=C=O, with each O atom having two lone pairs

Question 19

Which of the following best describes the Clausius-Clapeyron equation?

Accepted Answer

$\ln\left(\frac{P_2}{P_1}\right) = -\frac{\Delta H_{vap}}{R}\left(\frac{1}{T_2} - \frac{1}{T_1}\right)$

General Chemistry Course Learning Objectives and Key Topics

Study Guide - Practice Questions

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