Advertisements
Advertisements
Question
Answer the following.
Using Raoult’s law, how will you show that ΔP = `"P"_1^0 "x"_2`? Where, x2 is the mole fraction of solute in the solution and `"P"_1^0` vapour pressure of pure solvent.
Advertisements
Solution
1. Raoult’s law expresses the quantitative relationship between vapour pressure of solution and vapour pressure of the solvent.
2. In solutions of nonvolatile solutes, the law is applicable only to the volatile solvent.
3. The law states that, “the vapour pressure of solvent over the solution is equal to the vapour pressure of pure solvent multiplied by its mole fraction in the solution.”
4. Suppose that for a binary solution containing solvent and one nonvolatile solute, P1 is the vapour pressure of solvent over the solution, x1 and x2 are the mole fractions of solvent and solute, respectively and `"P"_1^0` is the vapour pressure of pure solvent, then, `"P"_1 = "P"_1^0 "x"_1`.
5. Since, x1 = 1 – x2,
`"P"_1 = "P"_1^0 "x"_1 = "P"_1^0 (1 - "x"_2) = "P"_1^0 - "P"_1^0 "x"_2`
∴ `"P"_1^0 - "P"_1 = "P"_1^0 "x"_2`
∴ `triangle "P" = "P"_1^0 "x"_2` (∵ Δ P is the lowering of vapour pressure)
Note: A plot of P1 versus x1 is a straight as shown below.
Variation of vapour pressure of solution with mole fraction of solvent
APPEARS IN
RELATED QUESTIONS
Choose the most correct option.
Vapour pressure of a solution is _______.
State Raoult’s law for the solutions of non-volatile solutes in volatile solvents.
Fish generally needs O2 concentration in water at least 3.8 mg/L for survival. What partial pressure of O2 above the water is needed for the survival of fish? Given the solubility of O2 in water at 0 °C and 1 atm-1 partial pressure is 2.2 × 10-3 atm mol/L.
What type of solutions exhibit positive deviations from Raoult’s law?
What is enthalpy change and volume change of mixing of two components forming an ideal solution?
The vapour pressures of pure liquids A and B are 0.600 bar and 0.933 bar respectively, at a certain temperature.
What is the mole fraction of liquid B in the solution when the total vapour pressure of their mixture is 0.8 bar?
What are non-ideal solutions?
Explain with reasons and diagrams, the positive and negative deviations from Raoult’s law shown by nonideal solutions.
Which of the following is NOT nonideal solution?
If 1 mole of ____________ is added to 1 dm3 of water, the boiling point of water will decrease.
A solution of acetone in ethanol ______.
18 g of glucose (C6H12O6) is added to 178.2 g of water. The vapour pressure of water for this aqueous solution at l00°C is ______.
What are ideal and non-ideal solutions?
The vapour pressures of two liquids A and B are 80 mmHg and 60 mm Hg respectively at 25°C. What is the vapour pressure of the solution obtained by mixing 3 moles of A and 2 moles of B?
A solution having highest vapour pressure is ______.
Explain the variation of vapour pressures with mole fractions of binary solutions of two volatile liquids forming ideal solutions.
State Raoult’s law for solutions containing volatile solutes.
The solutions that obey Raoult's law over entire range of concentrations are ______.
Which one of the following is not correct for an ideal solution?
