MCAT Physical : Reaction Calculations and Limiting Reagent
Study concepts, example questions & explanations for MCAT Physical
All MCAT Physical Resources
Example Questions
Example Question #51 : Stoichiometry And Analytical Chemistry
Consider the hydrolysis of acetyl chloride into acetic acid and hydrochloric acid:
If 1g of acetyl chloride is added to water, how much hydrochloric acid is produced?
The limiting reagent in this reaction is the acetyl chloride (because water is never the limiting reagent; there is always an excess of water). To solve this question, we need to convert the mass of acetyl chloride to moles. The molecular weight of acetyl chloride is:
The moles of acetyl chloride is:
The moles of hydrochloric acid produced is:
The molecular weight of 
Example Question #52 : Stoichiometry And Analytical Chemistry
1g of A is added to 1g of B and the following reaction occurs.
The total amount of products produced is 0.016mol. What is the identity of A and B and what is the limiting reagent?
Molecule A: sodium chloride
Molecule B: potassium iodide
Limiting reagent: potassium iodide
Molecule A: sodium chloride
Molecule B: potassium bromide
Limiting reagent: sodium chloride
Molecule A: sodium chloride
Molecule B: potassium iodide
Limiting reagent: sodium chloride
Molecule A: sodium chloride
Molecule B: potassium bromide
Limiting reagent: potassium bromide
Molecule A: sodium chloride
Molecule B: potassium bromide
Limiting reagent: potassium bromide
The question states that the total amount of products produced is 
Molecule A is sodium chloride and molecule B is potassium bromide. The molecular weight of sodium chloride is 
moles of molecule A =
moles of molecule B =
Since it has the lower amount of moles, molecule B is the limiting reagent. We can now calculate the moles of products produced.
moles of product C =
moles of product D =
The calculated amounts matches with the information given in the question; therefore, molecule A is sodium chloride, molecule B is potassium bromide, and the limiting reagent is potassium bromide.
If we follow this procedure for the other answer choices we will notice that the results don’t match with the given information.
Example Question #53 : Stoichiometry And Analytical Chemistry
A researcher runs an acid-base reaction using 3g of hydrochloric acid and 5g of cesium hydroxide. He wants to use the excess cesium hydroxide for another reaction. How much excess cesium hydroxide can he obtain after the completion of the reaction?
The first step is to determine the limiting reagent. To do this we need to first calculate the moles of reactants. The MW of hydrochloric acid is 
Next step is to write out the balanced chemical reaction
The ratio of reactants is 1:1; therefore, since 
All MCAT Physical Resources
