Chapter 4, Problem 4.137P

(a)

Interpretation Introduction

Interpretation:

The mass percentage of $\text{Mg}$ in a magnesium-aluminium alloy that has a mass of $0.263\text{ g}$ is to be determined.

Concept introduction:

Mass percent is employed to determine the concentration of one compound in a mixture of the compound. The formula to calculate mass percent is as follows:

$\text{Mass percent of compound}=\left(\frac{\text{mass of the compound}}{\text{mass of mixture}}\right)$

(b)

Interpretation Introduction

Interpretation:

The mass percentage of $\text{Mg}$ in a magnesium-aluminium alloy that reacts with excess aqueous $\text{HCl}$ and forms $1.38\times {10}^{-2}\text{mol}{\text{H}}_2$ is to be determined.

Concept introduction:

Stoichiometry of a reaction is utilized to determine the amount of any species in the reaction by the relationship between the reactants and products.

Consider the general reaction,

$\text{A}+2\text{B}\to 3\text{C}$

One mole of $\text{A}$ reacts with two moles of $\text{B}$ to produce three moles of $\text{C}$. The stoichiometric ratio between A and B is 1:2, the stoichiometric ratio between A and C is 1:3 and the stoichiometric ratio between B and C is 2:3.

(c)

Interpretation Introduction

Interpretation:

The mass percentage of $\text{Mg}$ in a magnesium-aluminium alloy that reacts with excess ${\text{O}}_2$ and forms $0.483\text{g}$ of oxide is to be determined.

Concept introduction:

Stoichiometry of a reaction is utilized to determine the amount of any species in the reaction by the relationship between the reactants and products.

Consider the general reaction,

$\text{A}+2\text{B}\to 3\text{C}$

One mole of $\text{A}$ reacts with two moles of $\text{B}$ to produce three moles of $\text{C}$. The stoichiometric ratio between A and B is 1:2, the stoichiometric ratio between A and C is 1:3 and the stoichiometric ratio between B and C is 2:3.