pclawong wrote:
We don't know the initial volume so how can we get the final volume?
Please explain, thank you
Alternatively you can use the following method:
We can solve this problem by equating the amounts of either A or B before and after evaporation.
CiVi = CfVf
As per the question, 20ml of A and 30ml of B have evaporated.
Lets solve for A.
(1)
Ci=4/9
(4/9) * x = Cf * (x-20)
We need to find x (total volume after 10 mins)
Since we do not have the value of Cf we cannot solve for x.
Insufficient
(2)
Cf=5/9
Ci * x = (5/9) * (x-20)
We need to find x (total volume after 10 mins)
Since we do not have the value of Ci we cannot solve for x.
Insufficient
(1) + (2)
Ci=4/9, Cf=5/9
(4/9) *x = (5/9) * (x-20)
Now we can solve for x
Ans : C
Hope it helps.