Question 1

Which of the following best describes the law of conservation of mass as it applies to chemical reactions?

Accepted Answer

The total mass of reactants must equal the total mass of products in a chemical reaction.

Question 2

Given the unbalanced equation $$\mathrm{C_2H_6} + \mathrm{O_2$} \rightarrow \mathrm{CO_2$} + \mathrm{H_2O}$$, what are the correct coefficients to balance the equation?

Accepted Answer

$$2, 7, 4, 6$$

Question 3

Which of the following is a correct net ionic equation for the reaction between aqueous solutions of silver nitrate and sodium chloride?

Accepted Answer

$$\mathrm{Ag^+}(aq) + \mathrm{Cl^-}(aq) \rightarrow \mathrm{AgCl}(s)$$

Question 4

Which of the following compounds is always soluble in water according to the general solubility guidelines?

Accepted Answer

$$\mathrm{Na_2SO_4}$$

Question 5

What is the oxidation number of sulfur in $$\mathrm{SO_2$}$$?

Accepted Answer

$$+4$$

Question 6

Which of the following reactions is a redox reaction?

Accepted Answer

$$\mathrm{Zn}(s) + \mathrm{$$CuSO_4$$}(aq) \rightarrow \mathrm{$$ZnSO_4$$}(aq) + \mathrm{Cu}(s)$$

Question 7

In the reaction $$\mathrm{2Na}(s) + \mathrm{Cl_2$}(g) \rightarrow 2\mathrm{NaCl}(s)$$, which substance is oxidized and which is reduced?

Accepted Answer

Na is oxidized, Cl$$_2 is $$reduced

Question 8

Which of the following best describes a spectator ion?

Accepted Answer

An ion that appears unchanged on both sides of a chemical equation

Question 9

A student mixes solutions of $$\mathrm{$$BaCl_2$$}$$ and $$\mathrm{Na_2SO_4}. $$What type of reaction occurs and what is the precipitate?

Accepted Answer

Precipitation reaction; $$\mathrm{$$BaSO_4$$}$$

Question 10

Which of the following is the correct balanced equation for the neutralization of sulfuric acid with sodium hydroxide?

Accepted Answer

$$\mathrm{H_2SO_4} + 2\mathrm{NaOH} \rightarrow \mathrm{Na_2SO_4} + 2\mathrm{H_2O}$$

Question 11

Assign the oxidation number to nitrogen in $$\mathrm{NO_3$^-}.$$

Accepted Answer

$$+5$$

Question 12

Which of the following statements about oxidation and reduction is correct?

Accepted Answer

Oxidation and reduction always occur together in a redox reaction.

Question 13

Which of the following is the correct net ionic equation for the neutralization of hydrochloric acid with sodium hydroxide?

Accepted Answer

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

Question 14

A solution contains $$\mathrm{K^+}$$, $$\mathrm{NO_3$^-}$$, $$\mathrm{Ag^+}$$, and $$\mathrm{Cl^-}. $$Which combination will form a precipitate?

Accepted Answer

$$\mathrm{Ag^+}$$ and $$\mathrm{Cl^-}$$

Question 15

Which of the following best describes a reducing agent in a redox reaction?

Accepted Answer

It loses electrons and is oxidized.

Question 16

In the reaction $$\mathrm{Cu}(s) + 2\mathrm{Ag^+}(aq) \rightarrow \mathrm{Cu$$^{2+}$$}(aq) + 2\mathrm{Ag}(s)$$, what is the oxidizing agent?

Accepted Answer

$$\mathrm{Ag^+}(aq)$$

Question 17

Which of the following is the correct sequence of steps for balancing a chemical equation?

Accepted Answer

Write correct formulas, add coefficients to balance atoms, check atom balance, reduce coefficients to lowest terms.

Chap 5: Classification and Balancing of Chemical Reactions: Study Notes for GOB Chemistry

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