RPAL Limiting Reagents 3

Question 1

In the reaction Fe + S → FeS, if 2 mol Fe and 3 mol S are present, how many moles of FeS can form?

Accepted Answer

2 mol

Answer

The 1:1 ratio means Fe (2 mol) is the limiting reagent, so only 2 mol FeS can be produced.

Question 2

How many moles of excess reagent remain after the reaction in the previous question (2 mol Fe + 3 mol S → FeS)?

Accepted Answer

1 mol S

Answer

Fe is limiting (2 mol), so 2 mol S is consumed, leaving 3 − 2 = 1 mol S unreacted.

Question 3

Which factor does NOT affect which reactant is the limiting reagent?

Accepted Answer

The temperature of the reaction

Answer

Temperature affects reaction rate and equilibrium but does not change which reactant runs out first based on mole quantities.

Question 4

For 2SO₂ + O₂ → 2SO₃, if 4 mol SO₂ and 1 mol O₂ react, how many moles of SO₃ are produced?

Accepted Answer

2 mol

Answer

O₂ is limiting (1 mol O₂ can react with 2 mol SO₂ per the 2:1 ratio), producing 2 mol SO₃.

Question 5

A recipe analogy for limiting reagent: if making sandwiches requires 2 slices of bread and 1 slice of cheese, and you have 10 bread and 4 cheese, what is the 'limiting reagent'?

Accepted Answer

Cheese

Answer

10 bread can make 5 sandwiches, but only 4 cheese are available, limiting production to 4 sandwiches — cheese is the limiting ingredient.

RPAL - Reactants, Products, and Leftovers Practice Test

RPAL - Reactants, Products, and Leftovers Practice Test

RPAL Limiting Reagents 3