Solids and Liquids [ENDORSED]

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McKenna_4A
Posts: 115
Joined: Sat Aug 24, 2019 12:18 am

Solids and Liquids

Why exactly aren't solids and liquids included in equilibrium expressions?

Fiona Latifi 1A
Posts: 102
Joined: Sat Sep 14, 2019 12:16 am

Re: Solids and Liquids  [ENDORSED]

Solids and liquids are considered pure substances. Therefore they have an activity value of 1. So in equilibrium expressions, we do not include them because their value would just be 1.

Wendy 1E
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Re: Solids and Liquids

It does not make sense for solids to have a concentration since the units for concentration are mol/L. For liquids, the change in concentration is insignificant because the change is very small.

Rebecca Remple 1C
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Re: Solids and Liquids

I agree with Fiona and McKenna! However, I am still confused on the matter of liquids being pure substancews. Can someone clarify how a liquid is different from an aqueous solution and give examples of each? From what I understand, aqueous solutions have a solute and solvent, and liquids do not. Can someone explain this a little more? Thank you!

-Rebecca

KHowe_1D
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Re: Solids and Liquids

They aren't calculated in equilibrium expressions because they are considered pure substances which don't affect the equilibrium concentration.

Donavin Collins 1F
Posts: 66
Joined: Sat Sep 14, 2019 12:16 am

Re: Solids and Liquids

Since solids and liquids are considered pure substances, they wouldn't affect the equilibrium concentration.

Posts: 107
Joined: Sat Aug 17, 2019 12:16 am
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Re: Solids and Liquids

Rebecca Remple 1C wrote:I agree with Fiona and McKenna! However, I am still confused on the matter of liquids being pure substancews. Can someone clarify how a liquid is different from an aqueous solution and give examples of each? From what I understand, aqueous solutions have a solute and solvent, and liquids do not. Can someone explain this a little more? Thank you!

-Rebecca

Liquidity is a state of matter where it can flow, takes the shape of its container, and has surface tension. Aqueous is a solution where water is the solvent. “Aqueous” means “similar to,” “related to,” or “dissolved in water.”

805394719
Posts: 104
Joined: Wed Sep 11, 2019 12:16 am

Re: Solids and Liquids

Solids and liquids are excluded from the equilibrium constant expression because their concentration equals their density divided by their molar mass. Since the density of a pure solid or liquid is constant regardless of how much solid or liquid is present, their concentrations stay constant throughout the reaction. Because their concentration does not change, they are not included in the equilibrium expression.

Rebecca Remple 1C
Posts: 137
Joined: Wed Sep 18, 2019 12:16 am
Been upvoted: 1 time

Re: Solids and Liquids

Rebecca Remple 1C wrote:I agree with Fiona and McKenna! However, I am still confused on the matter of liquids being pure substancews. Can someone clarify how a liquid is different from an aqueous solution and give examples of each? From what I understand, aqueous solutions have a solute and solvent, and liquids do not. Can someone explain this a little more? Thank you!

-Rebecca

Liquidity is a state of matter where it can flow, takes the shape of its container, and has surface tension. Aqueous is a solution where water is the solvent. “Aqueous” means “similar to,” “related to,” or “dissolved in water.”

Hi Kayla,

Thank you so much for your explanation! It helps a lot :) Good luck on the test and have a great weekend!

-Rebecca

Sanjana Borle 2K
Posts: 111
Joined: Fri Aug 09, 2019 12:15 am

Re: Solids and Liquids

Also for solids and liquids, pressure does not affect them, in other words they can't be compressed further, whereas gases can.

Matthew Tsai 2H
Posts: 101
Joined: Wed Sep 18, 2019 12:20 am

Re: Solids and Liquids

Regardless of conditions, solids and liquids will be pure substances with a concentration of 1, so for calculating the equilibrium constant of a reaction, they would have no effect.

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