$ x = \sqrt{K_a \cdot C} = \sqrt{1.8 \times 10^{-5} \times 0.500} = 3.0 \times 10^{-3} $; $\mathrm{pH} = -\log(3.0 \times 10^{-3}) = 2.52 $

$ 80 \times (\frac{1}{2})^{3} = 10\ \text{grams} $

Question 1

Which of the following best describes the difference between a physical and a chemical change?

Accepted Answer

A chemical change results in the formation of new substances, while a physical change does not alter the chemical identity.

Question 2

A sample of gas occupies 2.50 L at 1.00 atm and 300 K. What will be its volume at 2.00 atm and 400 K? (Assume ideal gas behavior.)

Accepted Answer

$ V_2 = \frac{P_1 V_1 T_2}{P_2 T_1} = \frac{(1.00)(2.50)(400)}{(2.00)(300)} = 1.67\ 	ext{L} $

Question 3

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 4

Which of the following best explains why ionic compounds tend to have high melting points?

Accepted Answer

The electrostatic attraction between oppositely charged ions is very strong.

Question 5

A 0.500 M solution of acetic acid ($\mathrm{CH_3COOH}$) has a $K_a$ of $1.8 	imes 10^{-5}$. What is the pH of the solution? (Assume $x \ll 0.500$)

Accepted Answer

$ x = \sqrt{K_a \cdot C} = \sqrt{1.8 	imes 10^{-5} 	imes 0.500} = 3.0 	imes 10^{-3} $; $\mathrm{pH} = -\log(3.0 	imes 10^{-3}) = 2.52 $

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

Which of the following best describes the trend in atomic radius across a period in the periodic table?

Accepted Answer

Atomic radius decreases from left to right due to increasing nuclear charge.

Question 8

A radioactive isotope has a half-life of 10 years. If you start with 80 grams, how much will remain after 30 years?

Accepted Answer

$ 80 	imes (\frac{1}{2})^{3} = 10\ 	ext{grams} $

Question 9

Which of the following is a correct Lewis structure for carbon dioxide ($\mathrm{CO_2}$)?

Accepted Answer

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

Question 10

Which of the following best explains why water is a polar molecule?

Accepted Answer

Water has a bent shape and an unequal distribution of electrons.

Question 11

Which of the following is the correct balanced chemical equation for the combustion of propane ($\mathrm{C_3H_8}$)?

Accepted Answer

$ \mathrm{C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O} $

Question 12

Which of the following statements about acids and bases is correct?

Accepted Answer

A strong acid completely ionizes in water, while a weak acid only partially ionizes.

Question 13

Which of the following is the correct electron configuration for a neutral atom of magnesium ($\mathrm{Mg}$, atomic number 12)?

Accepted Answer

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

Question 14

Which of the following best describes the process of nuclear fission?

Accepted Answer

A heavy nucleus splits into two lighter nuclei, releasing energy.

Question 15

Which of the following is the correct formula for calculating the molarity of a solution?

Accepted Answer

$ M = \frac{	ext{moles of solute}}{	ext{liters of solution}} $

Question 16

Which of the following best explains 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 17

Which of the following is the correct IUPAC name for $\mathrm{CH_3CH_2COOH}$?

Accepted Answer

Propanoic acid

Question 18

Which of the following best describes the role of a buffer solution?

Accepted Answer

A buffer solution resists changes in pH when small amounts of acid or base are added.

Question 19

Which of the following is the correct expression for the equilibrium constant ($K_{eq}$) for the reaction $aA + bB \rightleftharpoons cC + dD$?

Accepted Answer

$ K_{eq} = \frac{[C]^c [D]^d}{[A]^a [B]^b} $

General Chemistry Core Competencies and Study Guide

Study Guide - Practice Questions