Question

The concept of determining which reactant is limiting and which is in excess is akin to determining the number of sandwiches that can be made from a set number of ingredients. Assuming that a cheese sandwich consists of 2 slices of bread and 3 slices of cheese,

1. determine the number of whole cheese sandwiches that can be prepared from 36 slices of bread and 51 slices of cheese.

2. Which of the two ingredients limits the number of sandwiches that can be made?

a. slices of cheese

b. slices of bread

3. What quantity of the ingredient in excess remains?

Answer 1

First we will define what is limiting reactant and excess reactant in chemistry.

Limiting reactant: Limiting reactant in a chemical reaction is a substance that is totally consumed when the reaction is complete, so it limits the amount of product formed as reaction cannot proceed without it.

Excess reactant: Excess reactant in a chemical reaction is the substance that is left when the reaction is complete. So it is present in more quantity .

Here we have taken the example of sandwiches to understand this concept better.

We are assuming that a cheese sandwich consist of 2 slices of bread and 3 slices of sandwich.

1) we are given 36 slices of bread and 51 slices of cheese .

As, 2 slices of bread make one sandwich

so, 36 slices of bread can make 36÷2 = 18 sandwiches.

As 3 slices of cheese can make 1 sandwich.

so, 51 slices of cheese can make 51÷3 = 17 sandwiches

so we can make only 17 sandwiches , as we have cheese only for 17 sandwiches . Although we have bread for 18 Sandwiches but cheese limits the number of sandwiches to 17.

2) a) slices of cheese limits the number of sandwiches that can be made

3) Ingredient in excess is bread as we can only make 17 sandwiches but breads are there for 18 Sandwiches.

As 1 sandwich requires 2 bread , so we have 2 bread in excess.