An aqueous solution of a non-volatile solute freezes at 272 . 4 K , while pure water freezes at 273 . 0 K . Determine the following: The lowering of vapour pressure of water at 298 K . (Given: K f = 1 . 86 K kg mol - 1 , K b = 0 . 512 K kg mol - 1 and vapour pressure of water at 298 K = 23 . 756 mm of Hg ).

The number of solvent molecules escaping into vapour phase gets reduced and as a result the pressure exerted by the vapour phase is also reduced. Given, Vapour pressure of water is 23 . 756 mm of Hg . The lowering of vapour pressure is P 0 - P s P 0 = 760 - 23 . 756 760 = 736 . 244 760 = 0 . 97 .

An aqueous solution of a non-volatile solute freezes at 272 . 4 K , while pure water freezes at 273 . 0 K . Determine the following: Boiling point of solution. (Given: K f = 1 . 86 K kg mol - 1 , K b = 0 . 512 K kg mol - 1 and vapour pressure of water at 298 K = 23 . 756 mm of Hg ).

The boiling point is the temperature for a particular liquid to boil at. Given, Pure water boils at 373 . 0 K . The molal elevation constant, K b = 0 . 512 K kg mol - 1 . m = ∆ T f K f = 273 - 272 . 4 K 1 . 86 K kg mol - 1 = 0 . 6 K 1 . 86 K kg mol - 1 = 0 . 32 m . ∆ T b = K b × m ⇒ 373 − T b = K b × m . 373 − 0 . 512 × 0 . 32 = T b . T b = 373 − 0 . 163 = 372 . 84 K .

An aqueous solution of a non-volatile solute freezes at 272 . 4 K , while pure water freezes at 273 . 0 K . Determine the following: The molality of solution. (Given: K f = 1 . 86 K kg mol - 1 , K b = 0 . 512 K kg mol - 1 and vapour pressure of water at 298 K = 23 . 756 mm of Hg ).

Molality is defined as the total moles of a solute contained in a kilogram of a solvent. Given, The non-volatile solute freezes at 272 . 4 K . Pure water freezes at 273 . 0 K . The molal depression constant, K f = 1 . 86 K kg mol - 1 . 0 − T f = i × K f × m . 273 − 272 . 4 = 1 . 86 × m . m = 0 . 6 1 . 86 = 0 . 32 m .

Determine the osmotic pressure of a solution prepared by dissolving 0 . 025 g of K 2 SO 4 in 2 litres of water at 25 ° C , assuming that K 2 SO 4 is completely dissociated. ( R = 0 . 0821 L atm K - 1 mol - 1 ; Mol . wt . of K 2 SO 4 = 174 g mol - 1 ).

Given, The mass of the solute is W 2 = 0 . 025 g . The molecular mass of the solute is M 2 = 174 g mol - 1 . The volume of the solution, V = 2 L . The gas constant, R = 0 . 0821 L atm K - 1 mol - 1 . The temperature, T = 25 ° C = 298 K . The osmotic pressure, π = W 2 × R × T M 2 × V . π = 0 . 025 × 0 . 0821 × 298 174 × 2 . π = 0 . 00176 atm = 1 . 76 × 10 - 3 atm .

MEDIUM

12th ICSE

IMPORTANT

Earn 100

A solution containing $1.23 g$ of calcium nitrate in $10 g$ of water, boils at $100.975 ° C$ at $760 mm of Hg$ . Calculate the Van’t Hoff factor for the salt at this concentration. ( $K_{b}$ for water $= 0.52 K kg {mol}^{- 1}$ , mol. wt. of calcium nitrate $= 164 g {mol}^{- 1}$ ).

Important Questions on Solutions

EASY

12th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 2 - Solutions>ICSE-2018>Q 1

An aqueous solution of urea freezes at

- 0 . 186^{o} C

K_{f}

for water

= 1.86 K kg {mol}^{- 1}

K_{b}

for water

= 0.512 K kg {mol}^{- 1}

. The boiling point of urea solution will be:

EASY

12th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 2 - Solutions>ICSE-2018>Q 2

Calculate the osmotic pressure of a solution prepared by dissolving $0.025 g$ of $K_{2} {SO}_{4}$ in $2.0$ litres of water at $25^{o} C$ assuming that $K_{2} {SO}_{4}$ is completely dissociated. (molecular weight of $K_{2} {SO}_{4}$ $= 174 g {mol}^{- 1}$ ).

HARD

12th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 2 - Solutions>ICSE-2018>Q 3

The freezing point of a solution containing

5.85 g

NaCl

100 g

of water is

- 3 \cdot 348^{o} C

. Calculate Van’t Hoff factor ‘

i

’ for this solution. What will be the experimental molecular weight of

NaCl

? (

K_{f}

for water

= 1 \cdot 86 K kg {mol}^{- 1}

)

EASY

12th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 2 - Solutions>ICSE-2018>Q 4

An aqueous solution containing

12.48 g

of barium chloride in

1000 g

of water boils at

100.0832 ℃

. Calculate the degree of dissociation of barium chloride.
(

K_{b}

for water

= 0.52 K Kg {mol}^{- 1}

)

HARD

12th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 2 - Solutions>ICSE-2019>Q 6

Calculate the boiling point of urea solution when

6 g

of urea is dissolved in

200 g

of water. (

K_{b}

for water

= 0.52 K kg {mol}^{- 1}

, boiling point of pure water

= 373 K

, molecular weight of urea

= 60

MEDIUM

12th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 2 - Solutions>ICSE-2019>Q 7

When $0.4 g$ of acetic acid is dissolved in $40 g$ of benzene, the freezing point of the solution is lowered by $0.45 K$ . Calculate the degree of association of acetic acid. Acetic acid forms dimer when dissolved in benzene. ( $K_{f}$ for benzene $= 5.12 K kg {mol}^{- 1}$ , atomic mass: $C = 12, H = 1, O = 16$ ).

MEDIUM

12th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 2 - Solutions>ICSE-2019>Q 8

A solution is prepared by dissolving $9.25 g$ of non-volatile solute in $450 mL$ of water. It has an osmotic pressure of $350 mm$ of $Hg$ at $27 ° C$ . Assuming the solute is non-electrolyte, determine its molecular mass. ( $R = 0.0821 L atm K^{- 1} {mol}^{- 1}$ ).

MEDIUM

12th ICSE

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR CHEMISTRY>Chapter 2 - Solutions>ICSE-2020>Q 9

The elevation in boiling point when $0.30 g$ of acetic acid is dissolved in $100 g$ of benzene is $0.0633 ° C$ . Calculate the molecular weight of acetic acid from this data. What conclusion can you draw about the molecular state of the solute in the solution? (Given $K_{b}$ for benzene $= 2.53 K kg {mol}^{- 1}$ , at. wt. of $C = 12, H = 1, O = 16$ ).

A solution containing 1.23 g of calcium nitrate in 10 g of water, boils at 100.975 °C at 760 mm of Hg. Calculate the Van’t Hoff factor for the salt at this concentration. (Kb for water =0.52 K kg mol-1, mol. wt. of calcium nitrate =164 g mol-1).

Important Questions on Solutions

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A solution containing $1.23 g$ of calcium nitrate in $10 g$ of water, boils at $100.975 ° C$ at $760 mm of Hg$ . Calculate the Van’t Hoff factor for the salt at this concentration. ( $K_{b}$ for water $= 0.52 K kg {mol}^{- 1}$ , mol. wt. of calcium nitrate $= 164 g {mol}^{- 1}$ ).