1. The temperature of water vapour released from the solution after facing boiling point elevation is ________
a) Equal to 100℃
b) Below 100℃
c) Above 100℃
d) Much larger than 100℃
Explanation: After the boiling point elevation has occurred and the solution now boils at a temperature above the normal and hence the steam ejected is also at that temperature, hence the steam is superheated.
2. The vapour released from the feed after being considerably concentrated is superheated steam.
a) True
b) False
Explanation: As boiling point is a colligative property, as the boiling point elevation has occurred and the solution now boils at a temperature above the normal and hence the steam ejected is also at that temperature, hence the steam is superheated.
3. The Boiling point elevation as the evaporation in an evaporator proceeds can be approximately measured by __________
a) Duhring’s rule
b) Arrhenius rule
c) Kozeny Carman rule
d) Sieder tate rule
Explanation: The verified rule known as the Duhring’s rule measures the value of BPE of a solution. The rule states that – the boiling point (BP) of a given solution has a linear function with the boiling point of that same solution’s solvent which is pure water at the same temperature and pressure.
4. To help coping with boiling point elevation in evaporators, which of the following can be done?
a) Increase the feed temperature to its boiling point
b) Use superheated steam at the temperature of maximum boiling point
c) Increase pressure
d) Reduce pressure
Explanation:To cope with the BPE problem, industries mostly use superheated steam with the maximum Boiling point to ensure evaporation till the very end of the operation.
5. Which one the following properties of fluid in not a colligative property?
a) Osmotic pressure
b) Surface tension
c) Boiling point elevation
d) Vapour pressure depression
Explanation:The four properties of fluid that are colligative in nature are –
i. Vapour pressure depression
ii. Boiling point elevation
iii. Melting point depression
iv. Osmotic pressure.
6. The vapour pressure of the solution ________ when the concentration of solutes increases.
a) Increases
b) Decreases
c) Remains same
d) Becomes zero
Explanation: The four properties of fluid that are colligative in nature are –
i. Vapour pressure depression
ii. Boiling point elevation
iii. Melting point depression
v. Osmotic pressure.
Hence the vapour pressure decreases on increasing concentration.
7. To cope with the change in vapour pressure with increasing concentration and considering the sensitivity of the solution to high temperatures, which one of the following step can be undertaken?
a) Increase the feed temperature to its boiling point
b) Use superheated steam at the temperature of maximum boiling point
c) Increase pressure
d) Reduce pressure
Explanation: If the temperature cannot be increased to the maximum considering sensitivity of feed, the only option we have is to reduce pressure as it would bring down the boiling point of the feed.
8. The Duhring’s rule is used to determine _______
a) Osmotic pressure
b) Surface tension
c) Boiling point elevation
d) Vapour pressure depression
Explanation: The Duhring’s rule is used to determine the boiling point of a solution at a particular concentration of solute by assuming that the relation between boiling point solution and solvent is a linear function.
9. The Duhring’s rule states that: The boiling point of a given solution is a _____ function of the boiling point of water at the same temperature.
a) Linear
b) Parabolic
c) Exponential
d) Quadratic
Explanation: The Duhring’s rule is used to determine the boiling point of a solution at a particular concentration of solute by assuming that the relation between boiling point solution and solvent is a linear function. It is also necessary to consider that the solution follows Roult’s Law.
10. What are the names of the axes in the plot by Duhring?
a) X –Concentration of solution, Y- Boiling Point of solution
b) X –Boiling Point of pure water, Y- Boiling Point of solution
c) X –Boiling Point of Solution, Y- Concentration of solution
d) X –Boiling Point of solution, Y- Boiling Point of pure water
Explanation:The Duhring’s plot is made between boiling point of pure water as the abscissa and boiling point of solution as the ordinate.