Chapter 3, Problem 3.43P

(a)

Interpretation Introduction

Interpretation: Moles of ${\text{Cr}}_{\text{2}}{\text{O}}_{\text{3}}$ required to form ${\text{421 g Cr}}_{\text{2}}{\text{S}}_{\text{3}}$ is to be calculated.

Concept introduction: The formula to convert mass in grams to moles is as follows:

  $\text{Number of moles}=\frac{\text{Given mass}}{\text{molar mass}}$

For some stoichiometric balanced equation; the reactant that is present in the smallest amount is consumed completely to form the product and thus governs the product formation.This reactant is known as limiting reactant.On the basis of the stoichiometric ratio by which substrates combine, moles of product formed from each reactant can be calculated.

(b)

Interpretation Introduction

Interpretation: Mass of ${\text{Cr}}_{\text{2}}{\text{O}}_{\text{3}}$ required to form ${\text{421 g Cr}}_{\text{2}}{\text{S}}_{\text{3}}$ is to be calculated.

Concept introduction: The formula to convert mass in grams to moles is as follows:

  $\text{Number of moles}=\frac{\text{Given mass}}{\text{molar mass}}$

The formula to convert moles to mass in grams is as follows:

  $\text{Mass}=\left(\text{Number of moles}\right)\left(\text{molar mass}\right)$