Hi, the question is:

Question

In an equilibrium diagram for a binary mixture, what does it mean for distillation if the relative volatility is low?

a)Separation of the components is easy
b)No separation of the components can be done
c)There is no difference of ease in the separation of the components
d)Separation of the components is difficult
e) The components in the mixture are not at equilibrium

if the relative volatility is more than 1, the separation is easier and if equal to 1, then the separation process is impossible since both components have same vapor pressure.

I know the answer is either b) or d),but not sure since both seem to be acceptable and don't know which is more accurate. Need your help. Thanks.

Answer 1

The question is sort of vague. I would ask your professor in the morning as to the definition of "low". Personally I would say that it is just more difficult since it does not specify that the relative volatility is one, it is just low. That is just an opinion. Hope that helps guide your process.

Answer 2

If the "low" volatility in the question means it is CLOSE to 1 (not equal to 1), then the answer is letter 'D' or 'separation of components is difficult. If it said "exactly equal to 1", then it's 'B'. But since it doesn't indicate anything, I'll go with letter D.

Relative volatility basically indicates the differences in volatility of the two components, and is also called the 'separation factor'. If the relative volatility is close to 1, then that means their volatility values are close to one another, therefore in distillation process it is difficult to separate them in one stage only. You need a lot of stages to separate them efficiently. However, if the relative volatility is high ( >1000 for instance), then complete separation is almost possible in one stage.

Hope this helps~ `u`