1. Use Dalton’s law / ideal gas law for a mixture

For a mixture of ideal gases in volume $V$ at temperature $T$,

$P V = n_{\text{total}} R T$

So,

$P = \frac{n_{\text{total}}RT}{V}$

Thus we only need the total number of moles.

2. Calculate moles of each gas

• Oxygen: given mass $=16\,\text{g}$, molar mass of $O_2 = 32\,\text{g mol}^{-1}$

$n_{O_2} = \frac{16}{32} = \frac{1}{2}$

• Nitrogen: given mass $=28\,\text{g}$, molar mass of $N_2 = 28\,\text{g mol}^{-1}$

$n_{N_2} = \frac{28}{28} = 1$

• Carbon dioxide: given mass $=44\,\text{g}$, molar mass of $CO_2 = 44\,\text{g mol}^{-1}$

$n_{CO_2} = \frac{44}{44} = 1$

3. Find total moles

$n_{\text{total}} = \frac{1}{2} + 1 + 1 = \frac{5}{2}$

4. Compute pressure

Using

$P = \frac{n_{\text{total}}RT}{V}$

we get

$P = \frac{\left(\frac{5}{2}\right)RT}{V} = \frac{5RT}{2V}$

5. Match with options

$\frac{5RT}{2V} = \frac{5}{2}\frac{RT}{V}$

This matches Option D.

6. Comparison with stored answer

Stored correct answer: D
Derived answer: D

So the derived answer agrees with the stored answer.