Limiting Reagents Quiz

What is a limiting reagent in a chemical reaction?

• A catalyst that speeds up the reaction

• The product formed in the reaction

• The reactant that is available in excess

• The reactant that is completely used up first, stopping the reaction

Answer explanation

The reactant that is completely used up first, stopping the reaction

Which method calculates the limiting reagent by comparing the mole ratio of the reactants used in the reaction?

• Approach 3

• Approach 4

• Approach 1

• Approach 2

Answer explanation

Approach 1 calculates the limiting reagent by comparing the mole ratio of the reactants used in the reaction.

What is the result when 2.40 g of Mg reacts with 10.0 g of O2?

• Both react completely

• No reaction occurs

• Mg is the limiting reagent

• O2 is the limiting reagent

Answer explanation

Mg is the limiting reagent because it will be completely consumed before all the O2 reacts, resulting in excess O2.

How much excess O2 is left when 2.40 g of Mg reacts with 10.0 g of O2?

• 2.40 g O2

• 8.42 g O2

• 1.58 g O2

• 10.0 g O2

Answer explanation

To find the excess O2, calculate the moles of Mg and O2, determine the limiting reactant (Mg), find the moles of O2 reacted, and subtract from the initial moles of O2 to get 8.42 g of excess O2.

What is the limiting reagent if 76.4 grams of C2H3Br3 were reacted with 49.1 grams of O2?

• C2H3Br3

• O2

• H2O

• CO2

Answer explanation

The limiting reagent is C2H3Br3 because it is completely consumed first, determining the maximum amount of product that can be formed.

In the reaction of SiO2 with H2F2, which is the limiting reagent?

• SiF4

• SiO2

• H2O

• H2F2

Answer explanation

In the reaction of SiO2 with H2F2, H2F2 is the limiting reagent because it will be completely consumed before SiO2, determining the amount of product formed.

What is the correct balanced chemical equation for the oxidation of magnesium?

• 2 Mg + 2 O2 -> 2 MgO

• Mg + 2 O2 -> MgO

• 2 Mg + O2 -> 2 MgO

• Mg + O2 -> MgO

Answer explanation

The correct balanced chemical equation for the oxidation of magnesium is 2 Mg + O2 -> 2 MgO, as it shows the correct stoichiometry of the reaction.

How much MgO is produced when 2.40 g of Mg reacts with 10.0 g of O2?

• 3.98 g MgO

• 2.40 g MgO

• 25.2 g MgO

• 10.0 g MgO

Answer explanation

To find the amount of MgO produced, calculate the moles of Mg and O2, determine the limiting reactant, then use stoichiometry to find the mass of MgO. The correct answer is 3.98 g MgO.

What happens when the reactants are not mixed in the correct stoichiometric proportions?

• One of the reactants will be entirely consumed while another will be left over

• The reaction will not occur

• The reaction will produce more products

• All reactants will be used up completely

Answer explanation

One of the reactants will be entirely consumed while another will be left over

What is the role of a limiting reagent in a chemical reaction?

• It speeds up the reaction

• It acts as a catalyst

• It determines when the reaction stops

• It decreases the yield of the product

Answer explanation

The role of a limiting reagent in a chemical reaction is to determine when the reaction stops.