August 22, 2019, 01:10:22 AM
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Topic: The Equilibrium Constant and Extent of Reaction  (Read 131 times)

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Offline Greek0000

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The Equilibrium Constant and Extent of Reaction
« on: August 11, 2019, 09:39:48 AM »
The Equilibrium Constant and Extent of Reaction
Solid AgCl and AgBr were each placed in 1.0 L of water in separate beakers. Are the following reactions product- or reactant-favored? When equilibrium is achieved, in which beaker will the concentration of silver ion be larger?

AgCl(s) ::equil::Ag+(aq)+Cl-(aq)   Kc=1.8x10-10
AgBr(s) ::equil::Ag+(aq)+Br-(aq)   Kc=3.3x10-13

Keq=[Ag+][Cl-]/[AgCl] = x2/(1.00-x)=1.8x10-10
and
Keq=[Ag+][Br-]/[AgBr] = x2/(1.00-x)=3.3x10-13

there must be something wrong with my math because I cannot get the number of moles correct at equilibrium. I found that using whole numbers doesn't work with a significant figure of 10 digits. I tried using a quadratic formula but I only got a whole value. The answer in the book says

concentration of sivler in the AgCl beaker (1.3x10-5 M) is greater than in the AgBr beaker (5.7x10-7 M). Both are reactant-favored.

Offline AWK

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Offline sunkal

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Re: The Equilibrium Constant and Extent of Reaction
« Reply #2 on: August 11, 2019, 05:20:04 PM »
Greek0000,

Your book seems to have big issues. In your other question I pointed out an issue. Here also, looking at your attachment, an issue becomes clear.

For the equilibrium AgCl (s) = Ag+ (aq) + Cl- (aq) Keq = Ksp = [Ag+]eq [Cl-]eq. [AgCl] will not appear in the denominator, since the molarity of a solid is a constant at a given temperature, similar to its density. Therefore, Keq = x2, not what the book shows after the ice table.

Incidentally, in the ice table they are not moles (like initial moles), but molarities (like initial molarity).

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