## Quiz 3 Prep #7, setting up ICE box

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Joined: Fri Sep 26, 2014 2:02 pm

### Quiz 3 Prep #7, setting up ICE box

Problem: For the following reaction, if the initial concentration of PCl3 (g) is 1.0M and x is the equilibrium concentration of P4 (g), what is the expression for the equilibrium constant? PCl3 <--> P4 + Cl2

I balanced the equation... 4PCl3 <--> P4 + 6Cl2

In setting up my ICE box, I realize that the initial for P4 is 0, and that you would add "x" to get your equilibrium value...I still don't understand what to add/subtract for the other components of the reaction? Would I add 6x for Cl2 and subtract 4x from PCl3 because of the stoichiometric coefficients?

Thank you!

904456845
Posts: 4
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Quiz 3 Prep #7, setting up ICE box

4PCl3 <---> P4 + 6Cl2
I: 1.0M 0 0
C: -4x +x +6x
E:1.0-4x +x +6x

the universal rule about ICE Box is that the ratios of "change" are the same as in the formula. Thus, the ratios: PCl3:P4:Cl2=4:1:6, are seen in the formula and the amount of change is the same.

RaquelAvalos1K
Posts: 35
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Quiz 3 Prep #7, setting up ICE box

The expression for the equilibrium constant would thus be:

(x)(6x)6 = Kp
(1-4x)4

Correct?

Christian Corrales 3I
Posts: 11
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Quiz 3 Prep #7, setting up ICE box

That is what I got.

VivianDing2G
Posts: 2
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Quiz 3 Prep #7, setting up ICE box

Is it Kp or Kc?

HelenMach 1J
Posts: 12
Joined: Fri Sep 26, 2014 2:02 pm

### Re: Quiz 3 Prep #7, setting up ICE box

Kc I believe (talks about equilibrium concentration instead of equilibrium partial pressures)