## What is Q again?

$E_{cell} = E_{cell}^{\circ}-\frac{RT}{nF}\ln Q$

Andrew Uesugi 3I
Posts: 38
Joined: Wed Sep 21, 2016 2:56 pm

### What is Q again?

So I understand Q is part of the Nernst equation.

What I'm confused about is what makes up Q again? When I look at the cell equation, do I just choose the ions or what?

Tyler_Ash_3C
Posts: 25
Joined: Wed Sep 21, 2016 2:57 pm
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### Re: What is Q again?

Q is the reaction quotient. Mathematically, it is represented by the fraction: [products]/[reactants]. At equilibrium Q is equal to K, the equilibrium constant of the reaction. Partial pressures for gases can be used in the formula instead of concentrations if this is given in the problem. Recall from the chapter on equilibrium that when considering Q and K, you only use the concentrations or partial pressures of aqueous solutions and gases. Also, remember that the molar ratio in front of each product or reactant represents the exponent that goes with it when plugging it in the to the formula for Q or K.

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