Consider the following gas phase reaction being carried out in a closed vessel at 25°C. 2A(g) 4B(g) + C(g) time (min) total pressure of the system (mm Hg) 30 300 600 The pressure of C(g) at 30 minutes time interval would be _______ mm Hg. (nearest integer)
A. A
For the given gas phase reaction: 2A(g) 4B(g) + C(g) Let the initial pressure of A(g) be P_0. At t = 0: P_A = P_0, P_B = 0, P_C = 0 At t = t: P_A = P_0 - 2p, P_B = 4p, P_C = p Total pressure at time t, P_t = P_0 - 2p + 4p + p = P_0 + 3p At t = , the reaction is complete, so P_A = 0 2p = P_0 p = P_0 2 Total pressure at t = , P_ = 4 ( P_0 2 ) + P_0 2 = 5P_0 2 Given P_ = 600 mm Hg: 5P_0 2 = 600 P_0 = 240 mm Hg At t = 30 min, P_t = 300 mm Hg: P_0 + 3p = 300 240 + 3p = 300 3p = 60 p = 20 mm Hg The pressure of C(g) at 30 minutes is p = 20 mm Hg. Answer: 20
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