Chapter 11, Problem 74A

Interpretation Introduction

Interpretation:

The reason for the statement that limiting reactant is the reactant having the lowest mass to be incorrect needs to be explained.

Concept introduction:

Mole is defined as the $6.02214\times {10}^{23}$ particles of any substance.

Mole ratio is the ratio of number of moles of product to the number of moles of reactant.

Explanation of Solution

The given statement is incorrect because the reaction is always following the concept of mole not mass. The reactant always reacts in the stoichiometry of moles.

Let’s take an example.

$CH4+2O\text{2}\to \text{CO2}\text{+}\text{2H2O}$

In balanced chemical equation the coefficients represent the stoichiometry of moles with which they combine to form product.

And number of moles depends on the molar mass of substance which may be high or low. According to the statement given, least mass does not mean that it produces less amount of product.

The limiting reactant is the reactant which produced less amount of product with respect to the other depending on the stoichiometry of the balanced chemical equation.

For the reaction taken in example, if 1 mol of each reactant is given, oxygen will be limiting because to react with 1 mol of methane, 2 moles of oxygen gas is required.