Molality is defined as the number of moles of the solute particles which dissolved in unit weight of the solvent. It can be represented by the symbol m . m = Number of moles of solute Mass of the solvent ( in kg ) m = n B W A ( kg ) ∵ n B = W B M B m = W B M B × 1000 W A Where W B and W A are the mass of solute and solvent, respectively.

A sample of drinking water was found to be contaminated with CCl 4 . The level of contamination was 8 . 5 ppm by mass. (Molecular mass of CCl 4 = 153 . 18 g · mol - 1 ) (i) Calculate the contamination level in mass percent. (ii) Calculate the contamination level in molality

i 85 × 10 - 4 m % ; ii 0 . 55 × 10 - 4 m

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$18 g$ glucose (molar mass $180 g {mol}^{- 1}$ ) is present in $500 {cm}^{3}$ of its aqueous solution. What is the molarity of the solution? What additional data is required If the molarity of the solution is also required to be calculated?

Important Questions on Solutions

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

Find molality of pure water

(H_{2} O = 18)

EASY

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

Define: Molality

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

An antifreeze solution is prepared from

222.6 g

of ethylene glycol

(C_{2} H_{6} O_{2})

and

200 g

of water. Calculate the molality of the solution. If the density of the solution is

1.072 g {mL}^{- 1}

, then what shall be the molarity of the solution?

EASY

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

Calculate the molality of

20 %

(by weight) potassium carbonate solution.

(K = 39, C = 12, O = 16)

HARD

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

A sample of drinking water was found to be contaminated with

{CCl}_{4} .

The level of contamination was

8.5 ppm

by mass. (Molecular mass of

{CCl}_{4} = 153.18 g \cdot {mol}^{- 1}

)
(i) Calculate the contamination level in mass percent.
(ii) Calculate the contamination level in molality

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

Molality of

30 %

\frac{W}{W}

aqueous solution of

NaOH

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

Define molality of a solution.

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

An antifreeze solution is prepared from

222.6 g

of ethylene glycol

(C_{2} H_{6} O_{2})

and

200 g

of water. Calculate the molality of the solution. If the density of the solution is

1.072 g {mL}^{- 1}

, then what shall be the molarity of the solution?

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

Calculate molality of

1 M

concentrated solution of

{NaNO}_{3}

if density of solution is

1.25 g {cm}^{- 3}

EASY

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

3.65 gm HCl

is dissolved in 500 gram water. Determine the molality of the solution.

HARD

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

An antifreeze solution is prepared from

222.6 g

of ethylene glycol

(C_{2} H_{6} O_{2})

and

200 g

of water. Calculate the molality of the solution. If the density of the solution is

1.072 g {mL}^{- 1}

, then what shall be the molarity of the solution?

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

3.0 g

of oxalic acid

[{({CO}_{2} H)}_{2} \cdot 2 H_{2} O]

is dissolved in a solvent to prepare a

250 mL

solution. The density of the solution is

1.9 g / mL

. The molality and normality of the solution, respectively, are closest to

EASY

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

In $214.2 g$ syrup of sugar, $34.2 g$ sugar ( $C_{12} H_{22} O_{11}$ ) is present. What will be the molality of sugar syrup? ( $C = 12, H = 1, O = 16$ ).

EASY

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

In a sample of drinking water, many impurities are found including chloroform, ${CHCl}_{3}$ , which are carcinogenic. The level of these impurities was $15 ppm$ (according to mass)

Find the molality of chloroform in this sample of water.

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

$4 g$ of Caustic soda (molar mass $40$ ) is dissolved in water and solution is made to $200 gm$ . Calculate the molality of the solution.

EASY

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

3.0

gram ethanoic acid in

50

gram benzene having _____ molality? (Atomic weights :

H = 1, C = 12, O = 16

HARD

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

To prepare a solution with molality of

0.1 mol {kg}^{- 1}

of ethanol in

100 g

of water, the mass of ethanol needed is (molecular weight of ethanol

= 46 g {mol}^{- 1}

)

EASY

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

2.82 gm

of glucose (Molecular mass= 180) is dissolved in

30 gm

of water. Calculate molality of the solution.

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

The density of

NaOH

solution is

1.2 g {cm}^{- 3} .

The molality of this solution is

m

(Round off to the Nearest Integer):
[Use : Atomic masses :

Na : 23.0 u O : 16.0 u

H : 1.0 u

Density of

H_{2} O : 1.0 g {cm}^{- 3}]

MEDIUM

Chemistry>Physical Chemistry>Solutions>Methods of Expressing Concentration of a Solution

3 \cdot 42 \times 10^{- 2} kg

Sugar (molar mass

342

) is dissolved in water to produce

234.2 g

of sugar syrup, what is the molality of sugar syrup ?

18 g glucose (molar mass 180 g mol-1) is present in 500 cm3 of its aqueous solution. What is the molarity of the solution? What additional data is required If the molarity of the solution is also required to be calculated?

Important Questions on Solutions

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$18 g$ glucose (molar mass $180 g {mol}^{- 1}$ ) is present in $500 {cm}^{3}$ of its aqueous solution. What is the molarity of the solution? What additional data is required If the molarity of the solution is also required to be calculated?