Limiting Reactants

Question 1

When does a reaction stop?

Answer 1

When all of one of the reactants is used up.

Question 2

When a reaction ends, any other reactants are said to be what?

Answer 2

Any other reactants are said to be in excess.

Question 3

What is the reactant that’s used up in a reaction called?

Answer 3

Limiting reactant.

Question 4

Why is the reactant that’s used up called a limiting reactant?

Answer 4

Because it limits the amount of product that’s formed.

Question 5

What is the amount of product formed directly proportional to?

Answer 5

The amount of limiting reactant used.

Question 6

Why is the amount of product formed directly proportional the amount of limiting reactant used?

Answer 6

Because if you add more of the limiting reactant there will be more reactant particles to take part in the reaction, which means more product particles (as long as the other reactants are in excess).

Question 7

How can you use a balanced chemical equation to work out the mass of product formed, from a given mass of a limiting reactant?

Answer 7

1) Write out the balanced equation.
2) Work out the Mr of the reactant and product you’re interested in.
3) Find out how many moles there are of the substance you know the mass of.
4) Use the balanced equation to work out how many moles they’ll be of the other substance (product).
5) Use the number of moles to calculate the mass.