Question

For a non-volatile solute:
(a)- vapour pressure of solution is more than vapour pressure of solvent
(b)- vapour pressure of solvent is zero
(c)- vapour pressure of solute is zero
(d)- all of the above

Answer 1

Hint : You may have noticed that while making tea at home, after mixing all the ingredients required when we boil it, it still retains all the flavors of tea leaves and the sweetness of sugar added. This happens due to the difference in the vapour pressure of the solvent (water here) and solute (tea leaves and sugar here).

Complete step by step solution :
A substance with higher vapour pressure evaporates more readily in comparison to a substance with a lower vapour pressure. Now that we already know this, let us define what are volatile and nonvolatile solutes.
A volatile solute (alcohol, for example) is defined as a solute that has a tendency to form a vapour at the boiling point of the solution or in other words a volatile solute has higher vapour pressure in comparison to the solvent. Therefore, it produces vapour.
A nonvolatile solute (the salt, for example) is defined as a solute that hasn't got any tendency to form a vapour at the boiling point of the solution or in other words a non-volatile solute has lower vapour pressure in comparison to the solvent, almost negligible. Therefore, it does not produce vapour.
So, the correct option is (c).

Note : In a solution, nonvolatile impurities can increase the boiling point. On the contrary volatile impurities can lower the boiling point of the solution. This is true only if they do not react with the solution.