Kp for the reaction NH4I(s)---->NH3(g)+HI(g) is 1/4 at a particular temperature. Above equilibrium is established by taking 4 moles of NH4I(s) in 100 litre container, then moles of NH4I(s) left in the container at equilibrium is
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Solution
Dear Student,
The relation of Kp and Kc is: Kp = Kc(RT)Δn Δn = 2 R = 0.082 T = 298 K 1/4 = Kc (0.082*298)2 Kc = 0.00042 For reaction,
[NH4I]
[NH3]
[HI]
Initial
0.04
0
0
Change
-x
+x
+x
Equilibirum
0.04-x
x
x
Kc = [NH3][HI]/[NH4I] 0.00042 = x2/(0.04-x) 0.0000168 - 0.00042x = x2 x2 + 0.00042x - 0.0000168 = 0 x = 0.004 At equilibrium, concentration of NH4I left = 0.04-0.004 = 0.036 M Moles of NH4I left = concentration*volume = 0.036*100 = 3.6 moles 3.6 moles of NH4I are left.