Question

0.5 mole of ${H_2}S{O_4}$ is mixed with 0.2 mole of $Ca{\left( {OH} \right)_2}$​. The maximum number of moles of $CaS{O_4}$ formed is:
A: 0.2
B: 0.5
C: 0.4
D: 1.5

Answer 1

The mole concept is very significant and useful in chemistry. It is actually the base of stoichiometry and it provides the best option to express the amounts of reactants as well as products that are consumed and formed during a chemical reaction.

Complete solution:
To calculate the number of moles, we generally use the following formula:
$Number{\text{ }}of{\text{ }}moles = \dfrac{{Given{\text{ }}mass{\text{ }}}}{{{\text{ M}}molecular{\text{ }}mass{\text{ }}of{\text{ }}the{\text{ }}given{\text{ }}species}}$
Alternatively, we can also depict the number of moles from the balanced chemical equation. The coefficients actually represent the number of moles which react, not just only molecules.
In the question we are given that ${H_2}S{O_4}$ reacts with $Ca{\left( {OH} \right)_2}$ to form $CaS{O_4}$. The balanced chemical equation can be written as follows:
${H_2}S{O_4} + Ca{(OH)_2} \to CaS{O_4} + 2{H_2}O$
This chemical equation indicates that 1 mole of ${H_2}S{O_4}$ reacts with 1 mole of $Ca{\left( {OH} \right)_2}$ to form 1 mole of$CaS{O_4}$.
In the question we are given 0.5 moles of ${H_2}S{O_4}$and 0.2 moles of $Ca{\left( {OH} \right)_2}$and we have to calculate the number of moles of $CaS{O_4}$formed.
This indicates that $Ca{\left( {OH} \right)_2}$is the limiting reagent in this case. We have seen in the aforementioned balanced chemical equation that 1 mole of $Ca{\left( {OH} \right)_2}$forms 1 mole of $CaS{O_4}$. That means 0.2 moles of $Ca{\left( {OH} \right)_2}$will lead to the formation of 0.2 moles of $CaS{O_4}$.

Hence, the maximum number of moles of $CaS{O_4}$formed is 0.2. Thus, the correct answer is Option A.

Note: A balanced chemical equation simply obeys the law of conservation of mass. Balancing the chemical equations is a significant guiding principle in chemistry. A balanced chemical equation helps you to predict the amount of reactants required and the amount of products formed.