Chapter F, Problem F.7E

(a)

Interpretation Introduction

Interpretation:

Molar mass of metal M has to be calculated if the mass percentage of metal M in oxide ${\text{M}}_{\text{2}}\text{O}$ is $88.8\%$.

Concept Introduction:

Mass percentage composition of the individual elements can be calculated if the formula of the compound containing the elements is known.  Mass percentage of an element is calculated using the formula given below;

    $\text{Mass}\text{percentage}\text{of}\text{element}=\frac{\text{mass}\text{of}\text{element}\text{in}\text{sample}}{\text{total}\text{mass}\text{of}\text{sample}}\times 100\%$

(b)

Interpretation Introduction

Interpretation:

The metal oxide ${\text{M}}_{\text{2}}\text{O}$ has to be named.

Concept Introduction:

Ionic compounds are named considering the cation and anion present in it.  The cation part is written first followed by the anion part.

Rules for naming ionic compounds:

• The cation and anion present in the ionic compound has to be identified.  Oxidation number of the cation has to be decided in order to cancel the charge of the negative anions.
• Cation is named first.  In case, if the metal belongs to transition metals, then the oxidation number is shown using Roman numeral and entered in parenthesis.
• Anion has to be named next.  If monoatomic anion is present, then the element name is ended with –ide.  If an oxoanion is present then suffix –ate is added for the ion that has large number of oxygen atoms and suffix –ite is added for the ion that has less number of oxygen atoms.  If the element can form a series of four oxoanions, then for the oxoanion having the less number of oxygen atoms, prefix hypo- is added and prefix per- is added if the oxoanion contains highest number of oxygen atoms.
• If water molecule is present in the formula of the ionic compound, then the word hydrate is added along with the Greek prefix that correspond to the number of water molecules present in it.