Flashcards · 9620 · A Level Topic 12

Equilibrium constant Kp for homogeneous systems (A Level) flashcards

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Mole fraction and partial pressure: Mole fraction of A = n(A) ÷ total moles of gas (no units). Partial pressure of A = mole fraction of A × total pressure.
Kp expression for 2NO₂(g) ⇌ 2NO(g) + O₂(g): Kp = p(NO)² × p(O₂) ÷ p(NO₂)². With pressures in kPa, units are kPa (Δn = +1).
How do you work out the units of Kp?: (pressure unit)^Δn, where Δn = moles of gaseous products − moles of gaseous reactants. No units if Δn = 0.
Effect of raising total pressure on Kp and on the equilibrium position: Kp is unchanged. The position shifts towards the side with fewer moles of gas.
Kp increases when the temperature rises. Is the forward reaction exothermic or endothermic?: Endothermic: the rise in temperature moved the equilibrium right, in the endothermic direction.
A gas mixture has 0.270 mol of one gas in 0.900 mol total at 250 kPa. Partial pressure of that gas?: Mole fraction = 0.270 ÷ 0.900 = 0.300; partial pressure = 0.300 × 250 = 75.0 kPa.