Writing reaction quotient or equilibrium expression

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Kyra Dingle 1B
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Joined: Fri Sep 29, 2017 7:04 am

Writing reaction quotient or equilibrium expression

Postby Kyra Dingle 1B » Mon Nov 27, 2017 5:12 pm

For writing the reaction quotient, Q, or equilibrium expression, K, when do we write it as partial pressure with the capital P then the molecule as a subscript in contrast to as a concentration with the molecule surrounded in brackets?
For example in 11.3, it asks to write the equilibrium expression K, and in the solution manual it shows that it is written as partial pressure, but in 11.9 the expression is written with concentrations. Is this because in 11.3, each molecule is in gas form, while in 11.9 although all the molecules are gas, we were asked for specifically Kc?

Guadalupe T 1E
Posts: 58
Joined: Fri Sep 29, 2017 7:04 am

Re: Writing reaction quotient or equilibrium expression

Postby Guadalupe T 1E » Mon Nov 27, 2017 5:15 pm

Yes, it depends on what the question is asking for, concentration of partial pressure.

Guadalupe T 1E
Posts: 58
Joined: Fri Sep 29, 2017 7:04 am

Re: Writing reaction quotient or equilibrium expression

Postby Guadalupe T 1E » Mon Nov 27, 2017 5:16 pm

I have a question regarding this, do we use the ideal gas law to convert between the partial pressure and concentration?

Michelle Steinberg2J
Posts: 73
Joined: Fri Sep 29, 2017 7:04 am

Re: Writing reaction quotient or equilibrium expression

Postby Michelle Steinberg2J » Mon Nov 27, 2017 5:34 pm

Kyra Dingle 1I wrote:For writing the reaction quotient, Q, or equilibrium expression, K, when do we write it as partial pressure with the capital P then the molecule as a subscript in contrast to as a concentration with the molecule surrounded in brackets?
For example in 11.3, it asks to write the equilibrium expression K, and in the solution manual it shows that it is written as partial pressure, but in 11.9 the expression is written with concentrations. Is this because in 11.3, each molecule is in gas form, while in 11.9 although all the molecules are gas, we were asked for specifically Kc?


I was about to ask the same question on here... does anyone know how to differentiate between using a capital P or using [] with no P? It doesn't ask for pressure in 11.3 but the solution manual uses the capital P with ().

Evelyn L 1H
Posts: 67
Joined: Fri Sep 29, 2017 7:05 am

Re: Writing reaction quotient or equilibrium expression

Postby Evelyn L 1H » Mon Nov 27, 2017 5:50 pm

I need clarification on the same question

Sara Varadharajulu
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Joined: Thu Jul 13, 2017 3:00 am
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Re: Writing reaction quotient or equilibrium expression

Postby Sara Varadharajulu » Mon Nov 27, 2017 6:10 pm

it depends on what the question is asking. if the states are all aqueous, you will need to write concentrations, so use brackets. if it is a gas you can write it as a partial pressure using P or as a concentration using brackets---this will depend on what the question is asking and the information is give. if only some of the phases are gas and others are aq, then you need to write concentration using brackets. you can only write it using partial pressure if all the phases are gas.


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