Equilibrium problem assistance?

[匿名]

2016-07-25 7:30 pm

Phosphine (PH3) decomposes at elevated temperatures yielding gaseous P2 and H2:

2 PH3(g) ↔ P2(g) + 3 H2(g) Kp = 398 at 875 K

If a vessel at 875 K initially contains all three gases, each at a partial pressure of 2.0 atm, calculate the reaction quotient in order to determine which of the following is true:

Select one:
A. reaction occurs to decrease the partial pressure of H2
B. reaction is at equilibrium
C. reaction occurs to increase the partial pressure of H2
D. reaction occurs to increase the partial pressure of PH3

**I calculated Qc to be 8 which is less than Kc so won't the reaction go from left to right to reach equilibrium, increasing the partial pressure of H2?

回答 (1)

不用客氣

2016-07-25 7:44 pm

✔ 最佳答案

Reaction quotient, Q = p(P₂)*p(H₂)³/p(PH₃)² = 2*2³/2² = 4 < 398

To establish equilibrium, the numerator must be increased and the denominator must be increased. In other words, more PH₃ decomposes to P₂ and H₂. Hence, the partial pressure of H₂ increases.

...... Answer : C. reaction occurs to increase the partial pressure of H₂

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