Choose the correct option for the total pressure (in atm.) in a mixture of 4 g O₂ and 2 g H₂ confined in a total volume of one litre at 0°C is : [Given R = 0.082 L atm mol⁻¹K⁻¹, T = 273 K]

**Step 1 – Identify the given data**
Mass of O₂ = 4 g
Mass of H₂ = 2 g
Total volume V = 1 L
Temperature T = 0 °C = 273 K
Ideal‑gas constant R = 0.082 L atm mol⁻¹K⁻¹

**Step 2 – Convert the masses to moles**
Molar mass of O₂ = 32 g mol⁻¹ → n(O₂) = 4 g / 32 g mol⁻¹ = 0.125 mol
Molar mass of H₂ = 2 g mol⁻¹ → n(H₂) = 2 g / 2 g mol⁻¹ = 1 mol

**Step 3 – Find the total number of moles in the mixture**
n_total = n(O₂) + n(H₂) = 0.125 mol + 1 mol = 1.125 mol

**Step 4 – Apply the ideal‑gas equation**

Insert the known values:

**Step 5 – Perform the calculation**
First compute R T: 0.082 × 273 = 22.386
Then multiply by n_total: 22.386 × 1.125 = 25.18425 ≈ 25.18

**Result**
The total pressure of the gas mixture is **25.18 atm**.