## Winter 2013 final Q4B

Blake_Panter_3D
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### Winter 2013 final Q4B

Can someone explain how to find the change in the concentrations of O2 for each droplet after 100s? The equations the solutions has don't make conceptual sense to me.

Andrew Nguyen 3G
Posts: 22
Joined: Wed Sep 21, 2016 2:59 pm

### Re: Winter 2013 final Q4B

Dr. Lavelle mentioned problem solving today in lecture and this is an example of what he is talking about. From what I know, I don't think we learned how to directly solve problems like these in the course reader before. But it makes sense that:

[Current] = [Initial] + [Change in initial]

So:

[O2] = [O2 initial] + [change in initial O2]

Flip both equations:

1 / [O2] = 1 / ([O2 initial] + [change in initial O2])

Since Q = [Products] / [Reactants] = 1 / [O2], plug in:

Q = 942.23 = 1 / ([.00117] + [Change in initial O2])

Rearrange and solve using algebra.

tapasyat
Posts: 6
Joined: Fri Sep 25, 2015 3:00 am

### Re: Winter 2013 final Q4B

Wait why is there a 1 for the product? How do we know it's not the other way around/0/any other number?

EllisJang2O
Posts: 18
Joined: Wed Sep 21, 2016 2:55 pm
Blake_Panter_3D wrote:Can someone explain how to find the change in the concentrations of O2 for each droplet after 100s? The equations the solutions has don't make conceptual sense to me.

If you look at the original equation 2Fe(s)+ 2H2O(l) + O2(aq) ---> 2Fe(OH)2(s), you'll know how to write Q because Q = [products]/[reactants]
Since liquids and solids are not included, Q = 1/[O2]