Percent Yield and Limiting Reactant

A limiting reactant is a reactant that.....

• runs out during a chemical reaction

• causes a reaction to stop

• determines the amount of products that can be made

• all of these

Tags

NGSS.HS-PS1-7

Identify the limiting and excess reactants in the reaction shown.

• N₂ is limiting and H₂ is excess. 

• H₂ is limiting and N₂ is excess. 

• NH₃ is both limiting and excess.

• There is no limiting reactant. 

Tags

NGSS.HS-PS1-7

What does the theoretical yield represent in a chemical reaction?

• The amount of reactant that remains unreacted

• The maximum amount of product that can be obtained, as calculated through stoichiometry

• The minimum amount of reactant needed for the reaction

• The actual amount of product obtained from the reaction

Answer explanation

The theoretical yield represents the maximum amount of product that can be obtained, as calculated through stoichiometry.

Tags

NGSS.HS-PS1-7

What is percent yield?

• The percentage of reactants that are converted into products

• The efficiency of a catalyst in a reaction

• The ratio of actual yield to theoretical yield, multiplied by 100%

• The percentage of product that decomposes back into reactants

Answer explanation

The ratio of actual yield to theoretical yield, multiplied by 100%

Tags

NGSS.HS-PS1-6

What can cause the actual yield to be lower than the theoretical yield?

• An excess of reactants

• Side reactions and purification steps

• Complete consumption of all reactants

• A highly efficient catalyst

Answer explanation

Side reactions and purification steps can cause the actual yield to be lower than the theoretical yield by leading to loss of product during the process.

How is the limiting reactant determined?

• By comparing the mole ratio of reactants to the mole ratio required by the balanced chemical equation

• By identifying the reactant with the highest molar mass

• By measuring the physical state of the reactants

• By calculating the total mass of the reactants

Answer explanation

The limiting reactant is determined by comparing the mole ratio of reactants to the mole ratio required by the balanced chemical equation.

What role does the mole ratio play in stoichiometry?

• It is used to convert between the masses of reactants and products

• It determines the speed of the reaction

• It indicates the temperature at which the reaction occurs

• It measures the pressure of gaseous reactants

Answer explanation

The mole ratio is used to convert between the masses of reactants and products in stoichiometry.

Tags

NGSS.HS-PS1-7

What happens when a reactant is in excess?

• It remains unreacted after the reaction is complete

• It increases the speed of the reaction

• It decreases the theoretical yield

• It becomes the limiting reactant

Answer explanation

When a reactant is in excess, it remains unreacted after the reaction is complete, as there are no more available molecules of the other reactant to react with.

Tags

NGSS.HS-PS1-7

What is percent yield?

• The ratio of the actual yield to the theoretical yield, multiplied by 100%.

• The percentage of the reactant that remains unreacted.

• The percentage of the product that decomposes during the reaction.

• The ratio of the theoretical reactant to the theoretical yield, multiplied by 100%.

Answer explanation

Percent yield is the ratio of the actual yield to the theoretical yield, multiplied by 100%.

In a lab, a scientist calculate he should produce 12.3 grams of product in his experiment. When he is finished collecting his product it weighs 10.1 grams. What is his percent yield?

• 82%
• 0.82%
• 10.1 %
• 100%