Look at the following hypothetical reaction: a+3b--> c+3d assume that the equation is balanced. in which of the following reactant mole ratios will reactant b be the limiting reagent? a) a: 4b b) a: 5b c) 2a: 7b d) a: b

d) A:B

Explanation: Limiting reagent is the reagent which limits the formation of products.

Excess reagent is the reagent which is present in excess in the reaction.

a) A:4B

As seen from the given equation, 1 mole of A reacts with 3 moles of B, thus (4-3)= 1 mole of B will remain and thus A is the limiting reagent and B is the excess reagent.

b) A:5B

As seen from the given equation, 1 mole of A reacts with 3 moles of B, thus (5-3)= 2 moles of B will remain and thus A is the limiting reagent and B is the excess reagent.

c) 2A:7B

As seen from the given equation, 1 mole of A reacts with 3 moles of B, thus 2 moles of A will react with 6 moles of B. Thus (7-6)= 1 mole of B will remain and is the excess reagent.

d) A: B

As seen from the given equation, 3 moles of B react with 1 mole of A, thus 1 mole of B will react with 0.33 moles of A and (1 - 0.33) =0.66 moles of A will remain as excess reagent. B is the limiting reagent.