Question 1

Which of the following statements best describes the difference between an isotope and an ion?

Accepted Answer

An isotope has the same number of protons but a different number of neutrons, while an ion has the same number of protons but a different number of electrons.

Question 2

A sample contains 75% $$^{35}\mathrm{Cl} ($$atomic mass = 34.97 u) and 25% $$^{37}\mathrm{Cl} ($$atomic mass = 36.97 u). What is the average atomic mass of chlorine in this sample?

Accepted Answer

$$35.97\ \mathrm{u}$$

Question 3

Which of the following molecules has the greatest lattice energy?

Accepted Answer

$$\mathrm{MgO}$$

Question 4

Which of the following best explains why $$\mathrm{H_2O}$$ has a higher boiling point than $$\mathrm{H_2S}$$?

Accepted Answer

$$\mathrm{H_2O}$$ forms hydrogen bonds, while $$\mathrm{H_2S}$$ does not.

Question 5

Which of the following electron configurations represents a noble gas?

Accepted Answer

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

Question 6

A 0.250 M solution of $$\mathrm{NaCl} is $$prepared by dissolving 14.6 g of $$\mathrm{NaCl} in $$water. What is the final volume of the solution in liters? ($$\mathrm{NaCl}$$ molar mass = 58.44 g/mol)

Accepted Answer

$$1.00\ \mathrm{L}$$

Question 7

Which of the following best describes the molecular geometry and bond angle of $$\mathrm{CH_4$}$$?

Accepted Answer

Tetrahedral, $$109.5^\circ$$

Question 8

Which of the following is the correct net ionic equation for the reaction between aqueous solutions of $$\mathrm{Na_2SO_4}$$ and $$\mathrm{$$BaCl_2$$}$$?

Accepted Answer

$$\mathrm{Ba$$^{2+}$$ (aq) + SO_4$^{2-} (aq) \rightarrow $$BaSO_4$$ (s)}$$

Question 9

Which of the following molecules contains the most polar bond?

Accepted Answer

$$\mathrm{HF}$$

Question 10

A sample of gas occupies 2.50 L at 300 K and 1.00 atm. What will be its volume at 600 K and 2.00 atm?

Accepted Answer

$$2.50\ \mathrm{L}$$

Question 11

Which of the following best explains why $$\mathrm{CO_2$} is $$nonpolar even though it contains polar bonds?

Accepted Answer

The molecule is linear and the bond dipoles cancel each other.

Question 12

Which of the following is always soluble in water?

Accepted Answer

$$\mathrm{$$NaNO_3$$}$$

Question 13

Which of the following intermolecular forces is present in all substances, regardless of polarity?

Accepted Answer

London dispersion forces

Question 14

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

It lowers the activation energy, increasing the reaction rate.

Question 15

Which of the following is the correct rate law for a reaction that is first order in $$\mathrm{A}$$ and second order in $$\mathrm{B}$$?

Accepted Answer

$$\mathrm{rate = k[A][B]^2}$$

Question 16

Which of the following best explains why $$\mathrm{MgO}$$ has a higher melting point than $$\mathrm{NaCl}$$?

Accepted Answer

$$\mathrm{MgO}$$ has ions with higher charges, resulting in stronger electrostatic attraction.

Question 17

Which of the following is the correct formula for ammonium sulfate?

Accepted Answer

$$\mathrm{(NH_4$)_2SO_4}$$

Question 18

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

Accepted Answer

Atomic radius decreases due to increasing effective nuclear charge.

Question 19

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

Accepted Answer

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

General Chemistry Exam Review: Key Concepts and Practice Problems

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