Chapter 14 Study Questions-Chemical Equations

When a chemical reaction occurs:

• atoms are rearranged.

• the law of conservation of mass is always obeyed.

• chemical properties of new substances are different from the original properties.

• All of these happen when a chemical reaction occurs

The principle of conservation of atoms is satisfied in a chemical equation when:

• all of the atoms involved in the equation have an oxidation number of 1+.

• the reactant side has the same number of each type of atom as the product side.

• the sum of the coefficients on the reactant side is the same as the sum of the coefficients on the product side.

• each atom on the product side has the same subscript that it had on the reactant side.

Which of the following is evidence that a chemical change has occurred?

• A material changes from liquid to solid.

• The temperature of a material changes from 10°C to 20°C.

• A material is hammered from a round shape to a flat shape.

• A material changes color from blue to red.

Identify the reactants

• CO2 and H2O

• CH4 and O2

• O2 and H2O

• CH4 and CO2

How many atoms of reactants are present?

• 4

• 5

• 6

• 7

To successfully prove the law of conservation of mass, which of the following conditions may be ignored?

• The mass of the reactants before the reaction must be determined.

• The mass of the products after the reaction must be determined.

• The chemical reaction must be exothermic.

• The reaction must be performed in a closed system.

When you activate an instant cold pack, water mixes with a chemical and the pack gets very cold. This is an example of:

• an endothermic reaction.

• an exothermic reaction.

• a combustion reaction.

• a combustion reaction.

Polymers are large molecules made up of repeating segments. They are formed through a series of:

• synthesis reactions.

• single-displacement reactions.

• combustion reactions.

• decomposition reactions.

Examples of exothermic reactions include all of the following EXCEPT:

• wood burning in a campfire.

• photosynthesis in a green plant.

• an operating alkaline battery.

• the flame on a gas stove.

Which arrow represents the energy released by the reaction?

• A

• B

• C

• D