Chapter 11.2, Problem 20SSC

Interpretation Introduction

Interpretation:

The method to determine the mass of liquid bromine required to react completely with given amount (in grams) of magnesium should be explained.

Concept introduction:

The ratio of mass of substance to its molar mass is said to be number of moles of that substance.

The ratio of amount of any two compounds involved in a chemical reaction in terms of mole is said to be mole ratio, and used as a conversion factor between reactants and products.

Explanation of Solution

In order to determine the mass of liquid bromine, ${\text{Br}}_{\text{2}}$ required to react completely with given amount (in grams) of magnesium, the following steps are followed:

• The balanced chemical equation is written for the reaction of bromine with magnesium. The coefficients from the balanced reaction is used to calculate the mole ratio of bromine and magnesium.
• The given mass of magnesium is divided by the molar mass of magnesium to calculate the number of moles of magnesium.
• The calculated number of moles of magnesium are used to calculate the number of moles of liquid bromine using the mole ratio determined from the balanced equation.
• Now, the obtained number of moles of liquid bromine are multiplied by the molar mass of bromine to convert moles of bromine to grams, the mass of liquid bromine.