化學反應方程式與平衡常數

2013-03-26 2:28 am

Gaseous phosphorous pentachloride decompose to phosphorous trichloride

and chlorine at a temperature where K=1.0X10^(-3)mole/L.Suppose 2.00 mole

of phosphorous pentachloride in a 2.00L vessel is allowed to come to

equilibrium. The concentration of phosphorous pentachloride will be about

(A)2.0M (B)0.1M (C)3.16X10^(-2) (D)0.12M

答案為(B) 求詳解~

回答 (1)

胡雪8°

2013-03-26 6:35 am

✔ 最佳答案

(A), (B), (C) and (D) are NOT the correctionanswer.
The answer should be 0.969 mol/L.

PCl5(g) ⇌ PCl3(g) + Cl2(g)

Initial concentration of PCl5, [PCl5]o =2.00/2.00 = 1.00 mol/L

Let y mol be the no. of moles of PCl5 that decomposes atequilibrium.
Then, at equilibrium :
[PCl5] = (1.00 - y) mol/L
[PCl3] = [Cl2] = y mol/L

K = [PCl3] [Cl2] / [PCl5]
y² / (1.00 - y) = 1.0 x 10⁻³
y² = 0.001 - 0.001y
y² + 0.001y - 0.001 = 0
y = [-0.001 + √(0.001² + 4 x 0.001)] / 2
y = 0.031

The concentration of PCl5, [PCl5] = 1.00 - 0.031 = 0.969 mol/L

參考: 胡雪

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