RPAL Mole Ratios 3

Question 1

For the reaction 2Al + 6HCl → 2AlCl₃ + 3H₂, how many moles of H₂ are produced from 4 mol HCl?

Accepted Answer

2 mol H₂

Answer

The HCl:H₂ ratio is 6:3 = 2:1, so 4 mol HCl produces 4 × (3/6) = 2 mol H₂.

Question 2

How many moles of Al are needed to produce 1 mol AlCl₃ in 2Al + 6HCl → 2AlCl₃ + 3H₂?

Accepted Answer

1 mol Al

Answer

The Al:AlCl₃ ratio is 2:2 = 1:1, so 1 mol AlCl₃ requires 1 mol Al.

Question 3

For 3H₂ + N₂ → 2NH₃, how many moles of N₂ are needed to produce 6 mol NH₃?

Accepted Answer

3 mol N₂

Answer

The N₂:NH₃ ratio is 1:2, so 6 mol NH₃ requires 6 × (1/2) = 3 mol N₂.

Question 4

Why are mole ratios central to all stoichiometry calculations?

Accepted Answer

They link the quantities of all substances in a reaction through the balanced equation

Answer

Mole ratios are the bridge between moles of any two species in a reaction, enabling all quantitative predictions in stoichiometry.

Question 5

For C₃H₈ + 5O₂ → 3CO₂ + 4H₂O, what is the mole ratio of C₃H₈ to CO₂?

Accepted Answer

1:3

Answer

The coefficients are 1 for C₃H₈ and 3 for CO₂, giving a mole ratio of 1:3.

RPAL - Reactants, Products, and Leftovers Practice Test