# Raoult's Law

## Trending Questions

**Q.**

QUESTION 2.156

Heptane and octane form an ideal solution. At 373 K, the vapour pressure of the two liquid components is 105.2 kPa and 46.8 kPa respectively. What will be the vapour pressure of a mixture of 26.0 g of heptane and 35 g of octane?

**Q.**

QUESTION 2.36

100 g of liquid A (molar mass 140 g mol−1) was dissolved in 1000 g of liquid B (molar mass 180 g mol−1). The vapour pressure of pure liquid B was found to be 500 torr. Calculate the vapour pressure of pure A and its vapour pressure in the solution if the total vapour pressure of the solution is 475 torr.

**Q.**

State Distribution Law and give its three applications.

**Q.**

Henry’s constant (in $kbar$) for four gases $\alpha ,\beta ,\gamma $and $\mathrm{\delta}$ in water at $298K$ is given below:

$\alpha $ | $\beta $ | $\gamma $ | $\phantom{\rule{1ex}{0ex}}\delta $ | |

${K}_{H}$ | $50$ | $2$ | $2\times {10}^{-5}$ | $0.5$ |

Density of water$={10}^{3}kg{m}^{-3}$ at $298\mathrm{K}$

This table implies that:

Solubility of $\mathrm{\gamma}$ at $308\mathrm{K}$ is lower than at $298\mathrm{K}$

The pressure of a $5.55$ molal solution of $\mathrm{\delta}$is $250\mathrm{bar}$

$\u0251$has the highest solubility in water at given pressure

The pressure of a $55.5$molal solution of $\mathrm{\gamma}$ is $1\mathrm{bar}$

**Q.**Two liquids 'A' and 'B' form an ideal solution. At 300K, the vapour pressure of a solution containing 1 mol of A and 3 mol of B is 550 mm Hg. At the same temperature if one more mole of B is added to this solution, the vapour pressure of the solution increases by 10 mm Hg. Determine the vapour pressure of 'A' and 'B' in their pure states.

- p∘A=400 mm Hg and p∘B=600 mm Hg

- p∘A=600 mm Hg and p∘B=400 mm Hg
- p∘A=300 mm Hg and p∘B=700 mm Hg
- p∘A=700 mm Hg and p∘B=300 mm Hg

**Q.**The vapour pressure of ethanol (A) and methanol (B) are 44.5mm Hg and 88.7mm Hg respectively. An ideal solution is formed at the same temperature by mixing 60 g of ethanol with 40 g of methanol. Calculate the total vapour pressure of the solution (PT) and the mole fraction of methanol in the vapour phase (YB)

- PT=88.33 mm Hg and YB=0.25
- PT=66.13 mm Hg and YB=0.25
- PT=88.33 mm Hg and YB=0.65
- PT=66.13 mm Hg and YB=0.65

**Q.**

The vapour pressure of pure benzene and toluene are 160 and 60 torr respectively. The mole fraction of toluene in vapour phase in contact with the equimolar solution of benzene and toluene is

0.50

0.6

0.27

0.73

**Q.**

QUESTION 2.34

Vapour pressure of water at 293K is 17.535 mm Hg. Calculate the vapour pressure of water at 293K when 25g of glucose is dissolved in 450 g of water.

**Q.**The molar volume of liquid benzene (density =0.877 g/mL) increases by a factor of 2750 as it vapourises at 20∘C and that of liquid toluene (density =0.867 g/mL) increases by a factor of 7720 at 20∘C. A solution of benzene and toluene at 20∘C has a vapour pressure of 46.0 torr. Find the mole fraction of benzene in the vapour above the solution.

- 0.449
- 0.26
- 0.73
- 0.551

**Q.**

8 g NaOH is dissolved in water to make one litre solution, its molarity is

0.8 M

0.4M

0.1 M

0.2 M

**Q.**Two liquids 'A' and 'B' have vapour pressure (in pure state) in the ratio p∘A:p∘B=1:3 at a certain temperature. Assume 'A' and 'B' form an ideal solution and the ratio of mole fractions of 'A' to 'B' in the vapour phase is 4 : 3. The the mole fraction of 'B' in the solution at the same temperature is:

- 15
- 23
- 45
- 24

**Q.**mass of naoh solution required (50% w/w ) to neutralize 2 litre of 1M h2so4 solution

**Q.**

At a given temperature, the total vapour pressure (in Torr) of a mixture of volatile components A and B is given by P = 120 - 75 XBhence vapour pressure of pure A and B respectively (in Torr) are -

120, 75

120, 195

75, 45

120, 45

**Q.**

The vapour pressure of Benzene at 25∘ is 639.7mm of Hg. The vapour pressure of a solution of benzene at same temperature is 631.9 mm of Hg. The molality of solution is:

0.156 mol/kg

0.125 mol/kg

1.56 mol/kg

None of these

**Q.**

What is a positive deviation from Raoults Law and its example?

**Q.**Benzene and toluene form nearly ideal solutions. At 20∘, the vapour pressure of benzene is 75 torr and that of toluene is 22 torr. The partial vapour pressure of benzene at 20∘ for a solution containing 78g of benzene and 46g of toluene in torr is

- 25
- 37.5
- 50
- 53.5

**Q.**

A mixture of one mole each of ${\mathrm{H}}_{2}$, $\mathrm{He}$ and ${\mathrm{O}}_{2}$each are enclosed in a cylinder of volume $V$ at temperature $T$. If the partial pressure of ${\mathrm{H}}_{2}$ is $2atm$, the total pressure of the gases in the cylinder is:

$6atm$

$14atm$

$38atm$

$22atm$

**Q.**43. Two liquid A And B on mixing produce warm solution which type of deviation from Raoult law does it show?

**Q.**Value of entropy change for non ideal soln showing negative deviation from raoults law

**Q.**55. The vapour pressure of 2.1% of an aqueous solution of a non electrolyte at 373 K is 755 mm calculate the molar mass of solute

**Q.**

Vapour pressure of a solution is:

- Directly proportional to the mole fraction of the solvent
- Inversely proportional to the mole fraction of the solute
- Inversely proportional to the mole fraction of the solvent
- Directly proportional to the mole fraction of the solute

**Q.**

What weight of sodium hydroxide is required to neutralize 100ml of 0.1N HCl

**Q.**

Which aqueous solution has minimum freezing point?

$0.01\mathrm{M}\mathrm{NaCl}$

$0.005\mathrm{M}{\mathrm{C}}_{2}{\mathrm{H}}_{5}\mathrm{OH}$

$0.005\mathrm{M}{\mathrm{MgI}}_{2}$

$0.005\mathrm{M}{\mathrm{MgSO}}_{4}$

**Q.**Which of the following statements about the composition of the vapour over an ideal 1: 1 molar mixture of benzene and toluene is correct? Assume that the temperature is constant at 25∘C. (Given, vapour pressure data at 25∘C. benzene = 12.8 kPa, toluene = 3.85 kPa )

- The vapour will contain equal amounts of benzene and toluene.
- The vapour will contain a higher percentage of toluene.
- The vapour will contain a higher percentage of benzene.
- Not enough information is given to make a prediction.

**Q.**lowering of vapour pressure due to a solute in 1 molal aqueous solution at 100 C 1) 13.44 torr 2) 14.12torr 3)312 torr 4)352torr

**Q.**

What is the relationship between degree of dissociation and molar conductivity?

**Q.**

What are the factors on which the colligative properties of a solution depend?

**Q.**

A solution contains one mole of alcohol and four moles of water. What are the mole fractions of water and alcohol?

1/4, 4/1

4/1, 1/4

4/5, 1/5

1/5, 4/5

**Q.**Consider a binary mixture of two ideal volatile liquids A and B having vapour pressure of 400 mm Hg and 600 mm Hg in their pure state.

What will be the mole fraction of component A in vapour phase (yA) if the total pressure (PT) of the solution is 500 mm Hg?

- 0.3
- 0.6
- 0.7
- 0.4

**Q.**Mixture(s) showing positive deviation from Raoult’s law at 35∘C is/are:

- carbon tetrachloride + methanol
- carbon disulphide + acetone
- benzene + toluene
- phenol + aniline