1. Consider an ideal vapour-liquid binary mixture, find the total pressure if the vapour pressure of A is 260 mmHg and the vapour pressure of B is 520 mmHg and the composition of A in mole fraction is 0.55.
a) 177 mmHg
b) 277 mmHg
c) 377 mmHg
d) 477 mmHg
Explanation: Total pressure = (vapour pressure of A * mole fraction) + vapour pressure of B*( 1- mole fraction) = 377 mmHg.
2. Guess the exact relation between the vapour phase mole fraction and relative volatility.
a) y= A*x/(1+x(A+1))
b) y= A*x/(1-x(A-1))
c) y= A*x/(1+x(A-1))
d) y= A*x/(1-x(A+1))
Explanation: A= (y/1-y)*((1-x)/x)
On rearranging, y= A*x/(1+x(A-1).
where, A – relative volatility.
3. Given the total pressure is 2 atm. Also the partial pressure of the two components in an ideal solution is 1 atm and 0.5 atm. It shows __________ deviation.
a) Positive
b) Negative
c) Neutral
d) None of the mentioned
Explanation: If the total pressure is greater than sum of partial pressure then it shows positive deviation.
4. If the vapour pressure of the two components in a binary mixture is same, then it is a________
a) Isotope
b) Azeotrope
c) Differential boiling point
d) None of the mentioned
Explanation: Azeotrope is a mixture with a same boiling point.
5. Minimum boiling azeotrope has_________
a) Large positive deviation
b) Less positive deviation
c) Large negative deviation
d) Less negative deviation
Explanation: The difference of vapour pressure is large it shows large positive deviation.
6. Alternative word of Azeotrope is a Differential-boiling point.
a) true
b) false
Explanation: Azeotrope is a constant boiling mixture since it component has the same boiling point.
7. Negative deviation is due to a total pressure less than the pressure obtained from Hendry’s law.
a) true
b) false
Explanation: Because the total pressure should be less than the pressure obtained from Rauolt’s law.
8. Azeotropic composition can be eliminated by
a) Changing pressure
b) Changing temperature
c) Changing volume
d) None of the mentioned
Explanation: As by changing the vapour pressure we can avoid the azeotropic composition because the Azeotrope formation is due to same vapour pressure of the components.
9. When the two liquid mixtures are completely insoluble then the total pressure of the mixture is
a) Sum of the vapour pressure
b) Sum of the partial pressure
c) Pressure cannot be determined
d) None of the mentioned
Explanation: If the mixture is soluble the partial pressure comes to the part.No liquid exist without pressure. Therefore, the pressure of the mixture can be determined by the sum of its vapour pressure as this concept is mostly useful for stream distillation.
10. Consider an insoluble mixture A and B; Find the Total pressure of the system
Vapour pressure of A= 50mmHg
Vapour pressure of B= 100 mmHg
a) 50 mmHg
b) 100 mmHg
c) 150 mmHg
d) 200 mmHg
Explanation: For an insoluble mixture, total pressure = sum of vapour pressure.