If Kc = 82 for the reaction below at 200.0 K, then what is the value of Kp? (R = 0.0821 L･atm/mol･K.) 2 NO₂ (g) ⇌ N₂O₄ (g)

Answer 1

A general formula expressing the relationship between K_p and K_c is

K_p = K_c(RT)^Δn

where Δn = moles of gaseous product – moles of gaseous reactant

For 2 NO₂ (g) ⇌ N₂O₄ (g)

Δn = 1 – 2 = –1

RT = (200)(0.0821) = 16.42

K_p = K_c(RT)^–1 = K_c/RT = 82/16.42 = 4.994

Answer (rounded to 2 significant figures)

K_p = 5.0