
Answer:
5.2 mol
Explanation:
Step 1: Given data
Step 2: Calculate the mole fraction of oxygen
We will use the following expression.
pO₂ = P × X(O₂)
X(Oâ‚‚) = pOâ‚‚ / P
X(Oâ‚‚) = 140 kPa / 530 kPa
X(Oâ‚‚) = 0.264
Step 3: Calculate the moles of oxygen
We will use the definition of mole fraction of oxygen.
X(Oâ‚‚) = n(Oâ‚‚) / n
n(O₂) = X(O₂) × n
n(O₂) = 0.264 × 7.0 mol
n(Oâ‚‚) = 1.8 mol
Step 4: Calculate the moles of nitrogen
The total number of moles is equal to the sum of moles of the individual gases.
n(Oâ‚‚) + n(Nâ‚‚) = n
n(Nâ‚‚) = n - n(Oâ‚‚)
n(Nâ‚‚) = 7.0 mol - 1.8 mol
n(Nâ‚‚) = 5.2 mol