A gaseous compound has a volume of 30 cm 3 at room temperature and pressure. If 0.035 g of the compound is collected, what is its molar mass?

At room temperature and pressure (r.t.p.), 1 mole of any gas occupies $24000 \text{ cm}^3$.
Given volume = $30 \text{ cm}^3$.

$$\text{Moles} = \frac{\text{Given Volume}}{\text{Molar Volume at r.t.p.}}$$ $$\text{Moles} = \frac{30 \text{ cm}^3}{24000 \text{ cm}^3/\text{mol}}$$ $$\text{Moles} = 0.00125 \text{ mol}$$

Given mass = $0.035 \text{ g}$.

$$\text{Molar Mass} = \frac{\text{Mass}}{\text{Moles}}$$ $$\text{Molar Mass} = \frac{0.035 \text{ g}}{0.00125 \text{ mol}}$$ $$\text{Molar Mass} = 28 \text{ g/mol}$$

Comparing this to the given options:
A: 14g
B: 32g
C: 28g
D: 56g

The calculated molar mass matches option C.

The final answer is $\text{C: 28g}$.