Given below are certain reactions. Identify the reaction for which Kp Kc.
- N2(g) + O2(g) 2NO(g)
- H2O(g) + CO(g) H2(g) + CO2(g)
- N2(g) + 3H2(g) 2NH3(g)
- H2(g) + I2(g) 2HI(g)
Answer
(3) N2(g) + 3H2(g) 2NH3(g)
Solution
Kp = Kc(RT) ng, where ng = moles of gaseous products − moles of gaseous reactants
∴ Kp Kc only when ng 0
(2) ng = 2 − 2 = 0; (4) ng = 2 − 2 = 0; (1) ng = 2 − 2 = 0
(3) ng = 2 − 4 = −2 ⇒ Kp = Kc(RT)-2 ⇒ Kp Kc
Answer: (3)