Why Ignore Liquid or Solid Volume When Calculating K

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gconcha
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Why Ignore Liquid or Solid Volume When Calculating K

Postby gconcha » Tue Jan 14, 2020 1:13 pm

Why is it that when calculating for the KP (aka the Equilibrium Constant via pressures), that we don't take into account the volume taken up by liquid or solids in the container with the gas? Since they're hard to compress, wouldn't that reduce the amount of volume available for the gases?

Rita Chen 1B
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Re: Why Ignore Liquid or Solid Volume When Calculating K

Postby Rita Chen 1B » Tue Jan 14, 2020 1:27 pm

I think one thing is that the activity of a solid or liquid is equal to 1, so it doesn’t affect the K constant. Also in terms of solids, it is not dissolved, so would not have a concentration and I think something similar can be said with liquids as well.

Vicki Liu 2L
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Re: Why Ignore Liquid or Solid Volume When Calculating K

Postby Vicki Liu 2L » Tue Jan 14, 2020 1:28 pm

Kp is calculated using partial pressures not volume. Liquids and solids are excluded from the expression because they are available in excess so their pressures do not change before and after equilibrium.

Jack Riley 4f
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Re: Why Ignore Liquid or Solid Volume When Calculating K

Postby Jack Riley 4f » Tue Jan 14, 2020 1:57 pm

Liquids and solids cannot be dissolved or have their pressures changed in solution so they are not factored in when calculating K.

BNgo_2L
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Re: Why Ignore Liquid or Solid Volume When Calculating K

Postby BNgo_2L » Tue Jan 14, 2020 5:10 pm

Liquids and Solids don't have/have minimal changes in pressures nor concentrations, so they are typically not involved in computing the equilibrium constant.

Jamie Lee 1F
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Re: Why Ignore Liquid or Solid Volume When Calculating K

Postby Jamie Lee 1F » Wed Jan 15, 2020 5:06 pm

Liquids and solids don't necessarily dissolve in solvent, which is a main component of "concentration", which is then the focus of equilibrium calculations.

Bilal Pandit 1J
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Re: Why Ignore Liquid or Solid Volume When Calculating K

Postby Bilal Pandit 1J » Wed Jan 15, 2020 5:34 pm

K is all about the concentrations, and the change in the liquid and solid-state is negligible so we can just ignore that.

RichBollini4G
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Re: Why Ignore Liquid or Solid Volume When Calculating K

Postby RichBollini4G » Wed Jan 15, 2020 7:37 pm

BNgo_2L wrote:Liquids and Solids don't have/have minimal changes in pressures nor concentrations, so they are typically not involved in computing the equilibrium constant.

very helpful, thank you


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