Question 1

Which of the following best describes a combustion reaction?

Accepted Answer

A reaction in which a substance combines with oxygen to form one or more oxygen-containing compounds and releases heat.

Question 2

Given the unbalanced equation for the combustion of methane: $$\mathrm{CH_4$(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g)}$$, what is the correct set of coefficients to balance the equation?

Accepted Answer

$$1, 2, 1, 2$$

Question 3

Why is it incorrect to change the subscripts when balancing a chemical equation?

Accepted Answer

Changing subscripts changes the identity of the substances involved in the reaction.

Question 4

In the balanced equation $$\mathrm{C_8H_{18}(l) + 25\ O_2$(g) \rightarrow 16\ CO_2$(g) + 18\ H_2O(g)}$$, how many moles of $$\mathrm{CO_2$}$$ are produced from 2 moles of $$\mathrm{C_8H_{18}}$$?

Accepted Answer

32 moles

Question 5

Which of the following is the correct state symbol for an aqueous solution?

Accepted Answer

$$(aq)$$

Question 6

A chemical reaction is best defined as:

Accepted Answer

A process in which one or more substances are converted into one or more different substances.

Question 7

If 17 moles of $$\mathrm{C_8H_{18}}$$ are combusted according to $$\mathrm{C_8H_{18}(l) + 25\ O_2$(g) \rightarrow 16\ CO_2$(g) + 18\ H_2O(g)}$$, how many moles of $$\mathrm{H_2O}$$ are produced?

Accepted Answer

306 moles

Question 8

Which of the following statements about balancing chemical equations is correct?

Accepted Answer

The number of atoms of each element must be the same on both sides of the equation.

Question 9

A reaction between aqueous calcium chloride and aqueous lithium phosphate produces solid calcium phosphate and aqueous lithium chloride. Which of the following is the correct balanced equation?

Accepted Answer

$$3\ \mathrm{$$CaCl_2$$(aq)} + 2\ \mathrm{Li_3PO_4(aq)} \rightarrow \mathrm{Ca_3$(PO_4$)_2(s)} + 6\ \mathrm{LiCl(aq)}$$

Question 10

Which of the following is NOT provided by a balanced chemical equation?

Accepted Answer

The actual mechanism of the reaction

Question 11

In a real-world scenario, the combustion of octane ($$\mathrm{C_8H_{18}}) in $$car engines produces carbon dioxide and water. If a car burns 23 L of $$\mathrm{C_8H_{18}} ($$density = 0.703 g/mL, molar mass = 114.22 g/mol), how many moles of $$\mathrm{CO_2$}$$ are produced? (Use the balanced equation: $$\mathrm{C_8H_{18}(l) + 25\ O_2$(g) \rightarrow 16\ CO_2$(g) + 18\ H_2O(g)})$$

Accepted Answer

2,270 moles

Question 12

Which of the following conversion factors can be derived from the equation $$\mathrm{C_8H_{18}(l) + 25\ O_2$(g) \rightarrow 16\ CO_2$(g) + 18\ H_2O(g)}$$?

Accepted Answer

$$\dfrac{16\ \mathrm{mol}\ CO_2$}{1\ \mathrm{mol}\ C_8H_{18}}$$

Question 13

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

Accepted Answer

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

Question 14

A student writes the following equation for the combustion of propane: $$\mathrm{C_3H_8(g) + 4\ O_2$(g) \rightarrow 3\ CO_2$(g) + 4\ H_2O(g)}. Is $$this equation balanced?

Accepted Answer

No, because the number of oxygen atoms is not equal on both sides.

Question 15

Which of the following is a correct statement about stoichiometry?

Accepted Answer

Stoichiometry is the numerical relationship between chemical quantities in a balanced chemical reaction.

Question 16

In the reaction $$\mathrm{CH_4$(g) + 2\ O_2$(g) \rightarrow CO_2$(g) + 2\ H_2O(g)}$$, what is the mole ratio of $$\mathrm{O_2$} to$$ $$\mathrm{H_2O}$$?

Accepted Answer

$$1:1$$

Question 17

A chemical equation is balanced when:

Accepted Answer

The number of atoms of each element is the same on both sides of the equation.

Question 18

Which of the following is a real-world consequence of not balancing chemical equations in industrial chemical manufacturing?

Accepted Answer

Incorrect reactant quantities may be used, leading to waste or incomplete reactions.

Chemical Reactions, Balancing Equations, and Stoichiometry

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