APCE Chemical Reactions & Stoichiometry

Question 1

What does the Law of Conservation of Mass state?

Accepted Answer

Mass is conserved in a chemical reaction.

Answer

Mass is created in a chemical reaction.

Answer

Mass is destroyed in a chemical reaction.

Answer

The mass of reactants is irrelevant.

Question 2

What is stoichiometry used for in chemical reactions?

Accepted Answer

To calculate the amounts of reactants and products.

Answer

To measure the energy released.

Answer

To calculate the volume of a gas produced.

Answer

To balance the chemical equation.

Question 3

What is the molar ratio in a balanced chemical equation?

Accepted Answer

The ratio of moles of reactants to moles of products.

Answer

The number of atoms in each element.

Answer

The volume of gases involved.

Answer

The mass of reactants.

Question 4

What is the limiting reagent in a chemical reaction?

Accepted Answer

The reactant that is used up first.

Answer

The reactant that is present in excess.

Answer

The product that is formed.

Answer

The reactant that does not react.

Question 5

What is the mole concept used for in stoichiometry?

Accepted Answer

To convert between mass, volume, and number of particles in a reaction.

Answer

To calculate the concentration of a solution.

Answer

To determine the color change of a reaction.

Answer

To measure the temperature of the reaction.

Question 6

What is the purpose of balancing a chemical equation?

Accepted Answer

To ensure the correct stoichiometric relationship between reactants and products.

Answer

To make the equation easier to understand.

Answer

To calculate the energy of the reaction.

Answer

To find the limiting reagent.

Question 7

What is a combustion reaction?

Accepted Answer

A reaction that produces heat and light, usually with oxygen.

Answer

A reaction between two nonmetals.

Answer

A reaction that produces an ionic compound.

Answer

A reaction that absorbs energy.

Question 8

What is the difference between empirical and molecular formulas?

Accepted Answer

Empirical formulas show the simplest ratio, while molecular formulas show the actual number of atoms.

Answer

Empirical formulas are more accurate than molecular formulas.

Answer

Molecular formulas are used for ionic compounds.

Answer

Empirical formulas are used for acids.

Question 9

What is the significance of stoichiometry in determining the yield of a reaction?

Accepted Answer

It helps calculate the theoretical yield and compare it with the actual yield.

Answer

It determines the temperature of the reaction.

Answer

It identifies the reaction mechanism.

Answer

It measures the speed of the reaction.