Question

Equal volume of oxygen and an unknown gas weight 3.00g and 7.50g, respectively. Which of the following is the unknown gas?

• A. $C{O}_2$
• B. $NO$
• C. $N{O}_2$
• D. $S{O}_3$

Answer 1

Answer: (D)

$S{O}_3$

1. $S{O}_3$ is the gas.

2.Moles of $O_2=\frac{3.00g}{32g/mol}=0.09375$ moles

3.We assume the $2$ gasses are measured at the same temp and pressure

so moles of unknown gas $=0.09375$ moles

4.Molar mass of the unknown gas = $\frac{7.5g}{0.0975moles}$

$=80g/mol$

5.The unknown is $S{O}_3$ gas.