### 11.89

Posted: **Sat Dec 09, 2017 2:24 pm**

by **Katie 1E**

How do we know that there is a coefficient 2 in front of A in this question by looking at the graph?

Also, why are the values for the pressure in part b divided by a hundred? Thanks!

### Re: 11.89

Posted: **Sat Dec 09, 2017 5:45 pm**

by **Rakhi Ratanjee 1D**

There is a coefficient 2 because when you compare the changes in pressure for A, B, and C, you find that the ratio is:

A:B:C

=10:5:10

=2:1:2

Therefore, there are 2 molecules of A, 1 molecule of B, and 2 molecules of C. The balanced chemical reaction would be:

2A(g) + B(g) <--> 2C(g)

To address why each value in Kc is divided by 100, the basic SI unit of pressure is atmospheres and the values on the graph are given in kilopascals. Therefore, the Kc has to be given in atmospheres, so each value is divided by 100, which is the approximate conversion.

1atm = 101.325 kPa