If the vapour pressure of pure solvent A is 17.5 mm and lowering of va...
The correct answer is option C
Relative lowering of vapour pressure:
= lowering of vapour pressure of solution/ vapour pressure of pure solvent
=0.0175/17.5=0.001
View all questions of this test
If the vapour pressure of pure solvent A is 17.5 mm and lowering of va...
If the vapour pressure of pure solvent A is 17.5 mm and lowering of va...
**Explanation:**
**Vapour Pressure:**
Vapour pressure is the pressure exerted by the vapour phase when a liquid is in equilibrium with its own vapour at a particular temperature. It depends on the nature of the liquid and the temperature.
**Raoult's Law:**
According to Raoult's law, the partial pressure of a component in a solution is directly proportional to its mole fraction in the solution. Mathematically, it can be expressed as:
P = P°X
Where P is the vapour pressure of the solution, P° is the vapour pressure of the pure solvent, and X is the mole fraction of the solvent.
**Relative Lowering of Vapour Pressure:**
The relative lowering of vapour pressure is defined as the ratio of the lowering of vapour pressure to the vapour pressure of the pure solvent. Mathematically, it can be expressed as:
Relative Lowering of Vapour Pressure = (P° - P)/P°
Where P° is the vapour pressure of the pure solvent and P is the vapour pressure of the solution.
**Given Data:**
- Vapour pressure of pure solvent A (P°) = 17.5 mm
- Lowering of vapour pressure of solution (P° - P) = 0.0175 mm
**Calculation:**
Relative Lowering of Vapour Pressure = (P° - P)/P°
Substituting the given values, we get:
Relative Lowering of Vapour Pressure = (17.5 - 0.0175)/17.5
Simplifying the expression, we get:
Relative Lowering of Vapour Pressure = 17.4825/17.5
Relative Lowering of Vapour Pressure ≈ 0.9983
Rounding off to three decimal places, the relative lowering of vapour pressure is approximately 0.998.
Since the question asks for the answer in scientific notation, we can write the relative lowering of vapour pressure as 0.001.
Therefore, the correct answer is option **C) 0.001**.