Good ventilation as a product of it is pure Cl2 gas
C. 50%
Unless the question is saying he only gets heads once, in which case it would be 0%. Or the coin could have 2 heads. Then it would be 100%.
But I'm pretty sure it's 50%.
3 I don’t know but it may be movement
According to the task, you are proveded with patial pressure of CO2 and graphite, and here is complete solution for the task :
At first you have to find n1 =moles of CO2 and n2 which are moles of C
<span>The you go :
</span>

n1 n2 0
-x -x +2x

After that you have to use the formula

Then you have to solve x, and for that you have to use <span>RT/V
And to find total values:</span>

I am absolutely sure that this would be helpful for you.
[ H+]=10-pH
it become
[H+]=0.1