Question 1

Which of the following best describes a balanced chemical equation?

Accepted Answer

An equation that has the same number of each type of atom on both sides and obeys the Law of Conservation of Mass.

Question 2

Given the unbalanced reaction: $$\mathrm{CH_4$(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g)}$$, what are the correct coefficients to balance the equation?

Accepted Answer

$$1, 2, 1, 2$$

Question 3

In the reaction $$4\mathrm{KO_2$(s) + 2CO_2(g) \rightarrow 3O_2(g) + 2K_2CO_3(s)}$$, what is the total number of oxygen atoms on the reactant side?

Accepted Answer

$$12$$

Question 4

Which of the following reactions is balanced?

Accepted Answer

$$\mathrm{2Al(s) + 6HCl(aq) \rightarrow 2AlCl_3(aq) + 3H_2(g)}$$

Question 5

If 4.0 mol of $$\mathrm{KO_2$}$$ reacts with excess $$\mathrm{CO_2$}$$, how many moles of $$\mathrm{O_2$}$$ are produced according to the balanced equation $$4\mathrm{KO_2$(s) + 2CO_2(g) \rightarrow 3O_2(g) + 2K_2CO_3(s)}$$?

Accepted Answer

$$3.0$$ mol

Question 6

A student attempts to balance the equation $$\mathrm{CH_4$(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g)}$$ and writes $$\mathrm{CH_4$(g) + O_2$(g) \rightarrow CO_2$(g) + 2H_2O(g)}. $$What is the error in this equation?

Accepted Answer

The number of oxygen atoms is not balanced.

Question 7

When balancing chemical equations, which type of atom should generally be balanced last?

Accepted Answer

Atoms in pure elements

Question 8

In the reaction $$4\mathrm{KO_2$(s) + 2CO_2(g) \rightarrow 3O_2(g) + 2K_2CO_3(s)}$$, what is the ratio of moles of $$\mathrm{KO_2$}$$ consumed to moles of $$\mathrm{K_2CO_3}$$ produced?

Accepted Answer

$$4:2$$

Question 9

Which statement about the Law of Conservation of Mass is correct when balancing chemical equations?

Accepted Answer

The total mass of reactants must equal the total mass of products.

Question 10

A reaction is written as $$\mathrm{Al(s) + 3HCl(aq) \rightarrow $$AlCl_3$$(aq) + 3H_2(g)}. $$What is the total number of chlorine atoms on the product side?

Accepted Answer

$$3$$

Question 11

Which of the following is a correct step in balancing chemical equations?

Accepted Answer

Balance atoms in compounds before atoms in pure elements.

Question 12

If a balanced equation contains a fractional coefficient, what should you do to obtain whole-number coefficients?

Accepted Answer

Multiply the entire equation by the denominator of the fraction.

Question 13

In the reaction $$\mathrm{Al(s) + 6HCl(aq) \rightarrow 2AlCl_3(aq) + 3H_2(g)}$$, how many moles of $$\mathrm{HCl}$$ are required to react with 2 moles of $$\mathrm{Al}$$?

Accepted Answer

$$6$$ moles

Question 14

Which of the following is NOT a reason why chemical equations must be balanced?

Accepted Answer

To ensure the reaction occurs faster.

Chemical Quantities and Aqueous Reactions: Balancing Chemical Equations

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