Chapter 10, Problem 195A

Interpretation Introduction

Interpretation:

The compound among TiO₂, Fe₂O₃ and Al₂O₃ having greatest percentage of oxygen by mass needs to be determined.

Concept introduction:

The percentage of an element in a compound can be calculated as follows:

Percentage of an element in a compound $\text{=}\frac{\text{Number of atoms}\times \text{Atomic mass of the element×100}}{\text{Molar mass of the compound}}\text{.}$

Answer to Problem 195A

Al₂O₃ has greatest percentage of oxygen by mass.

Explanation of Solution

Molar mass of TiO₂ is 79.866 g/mol.

Molar mass of Fe₂O₃ is 160 g/mol.

Molar mass of Al₂O₃ is 102 g/mol.

Atomic mass of O is 16 g/mol.

Now, the mass percent of O in all the compounds will be:

% of O in TiO₂$\text{=}\frac{\text{2}\times \text{16×100\%}}{79.866}=\frac{3200}{79.866}\%=40.07\%.$

% of O in Fe₂O₃$\text{=}\frac{\text{3}\times \text{16}\times \text{100\%}}{160}=\frac{4800}{60}\%=30\%$

% of O in Al₂O₃$\text{=}\frac{2\times 27\times \text{100\%}}{102}=\frac{5400}{102}\%=52.94\%$

Conclusion

Thus, Al₂O₃ has largest % of O by mass.