# Molality

## Trending Questions

**Q.**

**QUESTION 2.8**

An antifreeze solution is prepared from 222.6 g of ethylene glycol (C2H6O2) and 200 g of water. Calculate the molality of the solution. If the density of the solution is 1.072 g m L−1, then what shall be the molarity of the solution?

**Q.**

If the density of some lake water is 1.25 g mL−1 and contains 92 g of Na+ ions per kg of water, calculate the molarity of Na+ ions in the lake.

**Q.**

Calculate the amount of benzoic acid (${\mathrm{C}}_{6}{\mathrm{H}}_{5}\mathrm{COOH}$) required for preparing 250 ml of 0.15 M solution in methanol.

**Q.**

Lowering of vapour pressure due to solute in 1 molal aqueous solution at 100°C is

BOOK ANSWER - 13.44 Torr

MY SOLUTION

Since molality is 1 mole kg^{-1}

That's mean 1 mole of solute is present in 1 kg of solvent (H_{2}O)

No. Of moles of Water = 1000g/18 = 55.55

No. Of moles of solute = 1

Mole Fraction of solute = 1/1+55.55 = 0.0176 .... (I)

Pressure of solvent (assuming ideal behaviour)

PV = nRT

P = 55.55 x 0.0821 x 373 / 1 (d of water = 1)

P = 1701.2774 atm

1 atm = 760 Torr

p_{solvent }= 1292970.8 Torr

We know from Raoult Law

∆p = X_{solute }. P(solvent)

∆p = 0.0176 x 1292970.8

∆p = 22756.286

So, According to my answer ∆p amount of vapour pressure will be low. But my answer and book answer is not same.

I don't want solution of this question.

You just tell me the place where I am going in wrong direction in my solution.

**Q.**mole fraction of ethanol water mixture 0.25 .hence percentage concentration by weight of mixture is 1.25% 2.75% 3.46% 4.54%

**Q.**

The vapour pressure of benzene at a certain temperature is 640mm of Hg. A non volatile and non electrolyte solid weighing 2.175 g is added to 39.08 g of benzene. The vapour pressure of the solution is 600mm of Hg. What is the molecular mass of the solid substance?

**Q.**

O2 is bubbled through water at 293K. How many moles of O2 will dissolve in 1L of water, if partial pressure of 02 is 2 kilobar and Kh is 34.86 kilobar?

**Q.**The boiling point elevation constant (Kb) of water is 0.52 K kg mol−1. The boiling point of 0.1 m aq. solution of urea is:

- 105.2∘C
- 1002.5∘C
- 100.52∘C
- 100.052∘C

**Q.**

Molarity of H2SO4 solution is 0.8M and its density is 1.06g/cm-3 What will be the concentration of the solution in terms of molality and determine the mole fraction of the solution

**Q.**Calculate the molality of a 20% CaCO3 solution (by mass). The density of the solution is 1.2 g/mL.

- 1.25 m
- 2.50 m
- 1.52 m
- 2.08 m

**Q.**Dissolving 120 g of urea (mol. wt. 60) in 1000 g of water gave a solution of density 1.15 g/mL. The molarity of the solution is

- 2.05 M
- 2.22 M
- 1.78 M
- 2.00 M

**Q.**

What is molality and molarity?

**Q.**

Question 2.29

Nalorphene (C19H21NO3), similar to morphine, is used combat withdrawal symptoms in narcotic users. Does of nalorphene generally given is 1.5 mg. Calculate the mass of 1.5×10−3 m aqueous solution required for the above dose.

**Q.**A solution of sodium sulfate contains 92 g of Na+ ions per kilogram of water. The molality of Na+ ions in that solution in molkg−1 is:

- 16
- 8
- 4
- 12

**Q.**

Assuming complete ionization, calculate freezing point of solution prepared by adding 6g Glauber's salt Na2SO4.10H2O in 0.1 kg of water ?(Given Kf = 1.86 K kg/mol , Atomic masses, Na=23, O=16, S=32, H=1 )

**Q.**

Find out the mole fraction of solute in an aqueous solution of $30\%\mathrm{NaOH}$.

**Q.**

4L of 0.02M aqueous solution of NaCl was diluted by adding 1L of water. The molality of the sol. Is

**Q.**Calculate the molality of 58.5 g of NaCl (Molar mass of NaCl= 58.5 gmol−1) dissolved in 500 g of water.

- 1 m
- 2 m
- 0.5 m
- 1.5 m

**Q.**Calculate the molality of an aqueous glucose solution in which mole fraction of glucose is 0.25.

- 20.64 m
- 18.26 m
- 13..88 m
- 18.52 m

**Q.**

36.5% HCl has density 1.20g/ml. The molarity and molality are..

**Q.**An aqueous solution ethanol has density 1.025 g mL−1 and 2 M. What is the molality of this solution?

- 2.143 m
- None of these
- 1.79 m
- 1.951 m

**Q.**

$2\mathrm{molal}$ solution of a weak acid $\mathrm{HA}$ has a freezing point of $3.885{}^{\mathrm{o}}\mathrm{C}$. The degree of dissociation of this acid is $\mathrm{\_\_\_\_\_\_\_\_\_}\times {10}^{\u20133}$. (Round off to the Nearest Integer). [Given: Molal depression constant of water $=1.85\mathrm{K}\mathrm{kg}{\mathrm{mol}}^{\u20131}$, Freezing point of pure water $=0{}^{\mathrm{o}}\mathrm{C}$]

**Q.**The density of a solution prepared by dissolving 120 g of urea (Mol. Mass =60 u) in 1000 g of water is 1.15 g/mol. The molarity of this solution is

(AIEEE 2012)

- 1.02 M
- 0.50 M
- 1.78 M
- 2.05 M

**Q.**Calculate the molality of a 1 L solution of 80% H2SO4(wv), given that the density of the solution is 1.80 g mL−1.

- 8.16 m
- 8.60 m
- 1.02 m
- 10.8 m

**Q.**The molality of a sulphuric acid solution is 0.2 mol/kg. Calculate the total weight of the solution having 1000 g, of solvent:-

- 1000 g
- 1098.6 g
- 980.4 g
- 1019.6 g

**Q.**Find the molality of 1 M HCl solution having a density of 1.5365 g/mL:

- 0.22 m
- 0.44 m
- 0.33 m
- 0.67 m

**Q.**Two liquid having vapour pressure P1 note and P2 note in pure state in the ratio of 2:1 are mixed in the molar ratio of 1:2.The ratio of their moles in the vapour state would be

**Q.**

According to the Raoult's law the relative decrease in the solvent vapour pressure over the solution containing a nonvolatile solute is equal to the

the mole fraction of the solute.

the viscosity of solution.

the number of moles of the solute.

the mole fraction of the solvent

**Q.**10L of urea solution contains 240g of urea. The active mass of Urea will be

- 0.04
- 0.02
- 0.2
- 0.4

**Q.**if mole fraction of urea in aqueous solution is 0.1 , then mass percentage of urea in the solution will be(molar mass of the urea 60g /mol