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J. W. Hill, R. H. Petrucci, T. W. McCreary, & S. S. Perry General Chemistry, 4th edition.

Problem 14.19

Determine the values of Kc that correspond to the following values of Kp.

(a) SO2Cl2(g) SO2(g) + Cl2(g)

Kp = 2.9×10–2 at 303 K

(b) 2 NO2(g) 2 NO(g) + O2(g)

Kp = 0.275 at 700 K

(c) CO(g) + Cl2(g) COCl2(g)

Kp = 22.5 at 395 oC






Answer:

In each case, find the change in the number of moles of gases between product and reactant and then use the relationship Kp = Kc(RT)n, where T is in K and R = 0.0821 L•atm/mol•K

(a) SO2Cl2(g) SO2(g) + Cl2(g) n = [1 + 1] – [1] = 1

Kp = 2.9×10–2 at 303 K so Kc = Kp/(RT)1 = 2.9×10–2/(0.0821×303)1 = 1.2×10–3

(b) 2NO2(g) 2NO(g) + O2(g) n = [2 + 1] – [2] = 1

Kp = 0.275 at 700 K so Kc = Kp/(RT)1 = 0.275/(0.0821×700)1 = 4.8×10–3

(c) CO(g) + Cl2(g) COCl2(g) n = [1] – [1 + 1] = –1

Kp = 22.5 at 395 oC = 668 K so Kc = Kp/(RT)–1 = Kp(RT)1 = 22.5(0.0821×668)1 = 1.23×103