Question 1

Which of the following is NOT considered macroscopic evidence of a chemical reaction?

Accepted Answer

The dissolution of sugar in water

Question 2

In the chemical equation $$\mathrm{CH_4$ + O_2$ \rightarrow CO_2$ + H_2O}$$, which substances are the reactants?

Accepted Answer

$$\mathrm{CH_4$}$$ and $$\mathrm{O_2$}$$

Question 3

What does the abbreviation $$(aq)$$ indicate in a chemical equation?

Accepted Answer

The substance is dissolved in water (aqueous solution)

Question 4

Which of the following best describes a combustion reaction?

Accepted Answer

A reaction in which a substance reacts with oxygen to form one or more oxygen-containing compounds, usually emitting heat

Question 5

Balance the following equation for the combustion of methane: $$\mathrm{CH_4$(g) + O_2$(g) \rightarrow CO_2$(g) + H_2O(g)}. $$What are the correct coefficients?

Accepted Answer

$$1, 2, 1, 2$$

Question 6

When balancing chemical equations, which of the following rules should you follow?

Accepted Answer

Change only the coefficients to balance the equation

Question 7

Which type of reaction is represented by the generic equation $$\mathrm{A + B \rightarrow AB}$$?

Accepted Answer

Synthesis (combination) reaction

Question 8

A student mixes two clear solutions and observes the formation of a cloudy solid. What type of reaction has most likely occurred?

Accepted Answer

Precipitation reaction

Question 9

Which of the following is the balanced equation for the reaction of aluminum with sulfuric acid to form aluminum sulfate and hydrogen gas?

Accepted Answer

$$\mathrm{2Al(s) + 3H_2SO_4(aq) \rightarrow Al_2$(SO_4$)_3(aq) + 3H_2(g)}$$

Question 10

Which of the following is a double-displacement reaction?

Accepted Answer

$$\mathrm{AB + CD \rightarrow AD + CB}$$

Question 11

A reaction in which a compound breaks down into simpler substances is called:

Accepted Answer

Decomposition reaction

Question 12

Which of the following observations is the ONLY absolute evidence of a chemical reaction?

Accepted Answer

Chemical analysis showing new substances are formed

Question 13

Which of the following reactions is a single-displacement reaction?

Accepted Answer

$$\mathrm{A + BC \rightarrow AC + B}$$

Question 14

If a chemical equation contains fractional coefficients, what should you do to obtain whole numbers?

Accepted Answer

Multiply the entire equation by the appropriate factor

Question 15

Which of the following is a correct balanced equation for the combustion of liquid methyl alcohol ($$\mathrm{CH_3OH}$$)?

Accepted Answer

$$\mathrm{2CH_3OH(l) + 3O_2(g) \rightarrow 2CO_2(g) + 4H_2O(g)}$$

Question 16

Which of the following is a redox reaction?

Accepted Answer

Combustion of methane

Question 17

Which element should be balanced LAST when writing a balanced chemical equation?

Accepted Answer

A free element

Question 18

Which of the following is a synthesis reaction?

Accepted Answer

$$\mathrm{2Na(s) + Cl_2$(g) \rightarrow 2NaCl(s)}$$

Question 19

Which of the following is a correct statement about combustion reactions involving hydrocarbons?

Accepted Answer

They always produce carbon dioxide and water as products

Question 20

Which of the following is the correct way to determine the number of atoms of an element in a chemical formula within an equation?

Accepted Answer

Multiply the subscript by the coefficient

Introduction to Chemical Reactions: Evidence, Equations, and States

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