Chemistry - Stoichiometry Question with Solution | TestHub

Question Explanation: Calculate the mass of oxygen consumed using the Law of Conservation of Mass. Concept:

Stoichiometry and Law of Conservation of Mass.

Solution: Let the total mass of the product mixture be W grams.

Mass of $\mathrm{CO}=0.40\mathrm{W}$; Mass of ${\mathrm{CO}}_2=0.60\mathrm{W}$. Mass of Carbon in $\mathrm{CO}=\frac{12}{28}\times 0.40\mathrm{W}=\frac{4.8\mathrm{W}}{28}$ Mass of Carbon in ${\mathrm{CO}}_2=\frac{12}{44}\times 0.60\mathrm{W}=\frac{7.2\mathrm{W}}{44}$

Total Carbon $=12\mathrm{g}$ (since all graphite reacted).

$\frac{4.8\mathrm{W}}{28}+\frac{7.2\mathrm{W}}{44}=12\Rightarrow \mathrm{W}\approx 35.8\mathrm{g}$ (Total Product Mass)

Mass of Oxygen $=$ Total Product Mass - Mass of Graphite

Mass of ${\mathrm{O}}_2=35.8\mathrm{g}-12\mathrm{g}=23.8\mathrm{g}$

Final Answer: Option (C)