Properties of Matter: Chemical Equations and Rates

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

____1. Which of the following changes is chemical rather than physical?

a. / Water is boiled. / c. / Glass is shattered.
b. / Aluminum foil is crumpled. / d. / Wood is burned.

____2. According to the law of conservation of mass, how does the mass of the products in a chemical reaction compare to the mass of the reactants?

a. / There is no relationship.
b. / The mass of products is sometimes greater.
c. / The mass of reactants is greater.
d. / The masses are always equal.

____3. When the following chemical reaction is balanced, what number is placed before NH3?

N2 + 3H2 → NH3

a. / 1 / c. / 3
b. / 2 / d. / 6

____4. Which chemical equation is balanced?

a. / Na + O2 → Na2O / c. / 2Na + 2O2 → 2Na2O
b. / 2Na2 + O2 → 2Na2O / d. / 4Na + O2 → 2Na2O

____5. Which one of the following factors would not speed up a chemical reaction?

a. / increasing the concentration of a reactant
b. / adding a catalyst
c. / raising the temperature
d. / lowering the temperature

____6. Which of the following materials will burn the fastest in open air?

a. / a log, two feet in diameter
b. / two logs, each one foot in diameter
c. / a pile of small splinters made from a two-foot diameter log
d. / Both logs and the splinters will burn at the same rate.

____7. A substance that speeds up chemical reactions in the human body is ____.

a. / an inhibitor / c. / polar
b. / an enzyme / d. / a prohibitor

Matching

Match each item with the best description below.

a. / physical change / h. / subscript
b. / conservation of mass / i. / endothermic
c. / chemical change / j. / inhibitor
d. / exothermic / k. / reactant
e. / product / l. / rate of reaction
f. / catalyst / m. / enzyme
g. / activation energy

____8.reaction that absorbs energy

____9.number of atoms in a chemical formula

____10.present before chemical reaction

____11.reaction that releases energy

____12.a measure of how fast a reaction occurs

____13.present after chemical reaction

____14.minimum energy to start reaction

____15.speeds up a chemical reaction

____16.used to slow the spoilage of food

____17.speeds up reactions in living cells

Short Answer

18.The following chemical reaction takes place: AgF + KCl → AgCl + KF. If 24 atoms of Ag react with 24 atoms of Cl, how many atoms of K must be present? Explain.

19.Distinguish a reactant from a product.

20.What is a catalyst?

21.What does an inhibitor do?

22.A chemical reaction is taking place between substance A and substance B. The reaction is taking place in two different containers, as shown in Figure 13-1. Compare the rates of reaction in containers I and II. Explain.

Figure 13-1

23. An iron nail (Fe) is placed into a solution of copper(II) sulfate (CuSO4). After some time, the blue color of the copper(II) sulfate disappears and some copper-colored solid (Cu) is found on the surface of the nail. The solution now contains iron(II) sulfate (FeSO4), and the container feels warmer than before the reaction.

a.List the reactants.

b. List the products.

c. Write a balanced chemical equation for this reaction.

d.Does this reaction absorb or release energy? How do you know?

e.What do the color changes indicate?

24. Label each of the following chemical reactions as endothermic or exothermic.

a. N2 + 3H2 + energy → 2NH3

b.Natural gas burns to heat a home.

c.H2 + Cl2 → 2HCl + energy