calculating reaction quotient

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Katherine Wu 1H
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calculating reaction quotient

Postby Katherine Wu 1H » Thu Jan 09, 2020 3:28 pm

Calculate the reaction quotient, Qc, from the following equilibrium data collected in a 3.00 L sealed reaction vessel for the reaction: AsH3 = 5.55 x 10^-4 mol, As= 3.31 x 10^-3 mol, H2= 1.23 x 10^-3 mol.
I keep getting the wrong answer when I try to solve this problem. Can someone show me how to actually solve this?

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Re: calculating reaction quotient

Postby Chem_Mod » Thu Jan 09, 2020 3:48 pm

It may be helpful to post your steps to see where you might have missed something! But first, write out the balanced chemical equation and set up your equilibrium expression. Make sure the exponents match the stoichiometric coefficients. Keep in mind that you should be using concentrations, so you would first have to divide the number of moles by the total volume before substituting values into your expression.

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Re: calculating reaction quotient

Postby DanielTalebzadehShoushtari2A » Thu Jan 09, 2020 3:48 pm

I would assume the balanced reaction is 2As + 3H2 <--> 2AsH3
From there, you would take the mol values for AsH3 and H2 and divide them each by 3.00 L to get the concentrations.
I am assuming that As is in solid form and that AsH3 and H2 are gases. Since As is solid, it is not included in the calculation for Q.
Then, you would calculate Q by doing [AsH3]^2 divided by [H2]^3
The answer might be the inverse depending on how the reaction is written.
If you can direct me to where you got this problem I might be able to help further. I hope this helps

Skyllar Kuppinger 1F
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Re: calculating reaction quotient

Postby Skyllar Kuppinger 1F » Thu Jan 09, 2020 5:21 pm

Make sure you are writing the balanced reaction. If they’ve given u a reaction in a problem, it might not be balanced already. Also, look out for any solids or liquids and make sure not to include them in the calculation. If you’re still getting it wrong then I would suggest posting a pic of your work so we can see your steps

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