Question 1

Which of the following is NOT an observable evidence of a chemical reaction?

Accepted Answer

Change in shape

Question 2

During a chemical reaction, what happens to chemical bonds?

Accepted Answer

Bonds are broken in reactants and formed in products

Question 3

Which of the following best describes the decomposition of sodium bicarbonate ($$\mathrm{$$NaHCO_3$$}) $$when heated?

Accepted Answer

It forms sodium carbonate, water, and carbon dioxide.

Question 4

What is the balanced chemical equation for the decomposition of sodium bicarbonate?

Accepted Answer

$$2\mathrm{$$NaHCO_3$$} (s) \rightarrow \mathrm{Na_2CO_3} (s) + \mathrm{H_2O} (l) + \mathrm{CO_2$} (g)$$

Question 5

Which symbol in a chemical equation represents a substance dissolved in water?

Accepted Answer

$$(aq)$$

Question 6

If a chemical reaction produces a gas, which observable evidence might you see?

Accepted Answer

Formation of bubbles

Question 7

Which of the following is a correct statement about chemical equations?

Accepted Answer

They use chemical formulas and symbols to represent chemical reactions.

Question 8

What does the symbol $$\Delta$$ above the arrow in a chemical equation indicate?

Accepted Answer

The reaction requires heat

Question 9

Which of the following changes is NOT a chemical change?

Accepted Answer

Melting of ice

Question 10

A student observes a reaction where a solid forms from two solutions. What is this evidence called?

Accepted Answer

Formation of a precipitate

Question 11

Which of the following best explains why chemical equations must be balanced?

Accepted Answer

To obey the law of conservation of mass

Question 12

In the reaction $$2\mathrm{$$NaHCO_3$$} (s) \rightarrow \mathrm{Na_2CO_3} (s) + \mathrm{H_2O} (l) + \mathrm{CO_2$} (g)$$, which product is released as a gas?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 13

Which of the following is a correct description of what happens at the molecular level during a chemical reaction?

Accepted Answer

Bonds are broken and new bonds are formed

Question 14

A reaction produces a temperature increase, a color change, and a gas. What type of change is this most likely?

Accepted Answer

A chemical change

Question 15

Which of the following is the correct symbol for a solid in a chemical equation?

Accepted Answer

$$(s)$$

Chemical Reactions: Evidence, Representation, and Symbolism

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