Solutions - Maharashtra Board STD 12 Science Chemistry Questions

$A 0.1 m$ solution of $K _2 SO _4$ in water has freezing point of $-0.43^{\circ} C$. What is the value of van't Hoff factor if $K_f$ for water is $1.86 K kg mol ^{-1}$ ?

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Q 7Answer the following in one or two sentence.2 Marks

A solution containing $10 g$ glucose has osmotic pressure $3.84 atm$. If $10 g$ more glucose is added to the same solution, what will be its osmotic pressure. (Temperature remains constant)

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Q 8Answer the following in one or two sentence.2 Marks

An organic substance $\left(M=169 gram mol ^{-1}\right)$ is dissolved in $2000 cm ^3$ of water. Its osmotic pressure at $12^{\circ} C$ was found to be $0.54 atm$. If $R =0.0821 L atm K ^{-1} mol ^{-1}$, calculate the mass of the solute.

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Q 9Answer the following in one or two sentence.2 Marks

A solution of a substance having mass $1.8 \times 10^{-3} kg$ has the osmotic pressure of $0.52 atm$ at $280 K$. Calculate the molar mass of the substance used.
[Volume $=1 dm ^3, R =8.314 JK ^{-1} mol ^{-1}$ ]

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Q 10Answer the following in one or two sentence.2 Marks

One litre of a solution containing $25 g$ glucose has osmotic pressure $3.4 atm$ at $300 K$. If by diluting the solution the osmotic pressure becomes $2.0 atm$ at the same temperature, what would be its concentration ? (Molar mass of glucose $=180)$

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Q 11Answer the following in brief.3 Marks

State Raoult’s law for a solution containing a nonvolatile solute.

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Q 12Answer the following in brief.3 Marks

What is the effect on the boiling point of water if 1 mole of methyl alcohol is added to $1 dm ^3$ of water? Why?

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Q 13Answer the following in brief.3 Marks

Anhydrous sodium sulphate dissolves in water with the evolution of heat. What is the effect of temperature on its solubility ?

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Q 14Answer the following in brief.3 Marks

Why naphthalene dissolves in benzene but not in water ?

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Q 15Answer the following in brief.3 Marks

While considering boiling point elevation and freezing point depression a solution concentration is expressed in molality and not in molarity. Why?

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Q 16Answer the following in detail.4 Marks

Arrange the following solutions in order of increasing osmotic pressure. Assume complete ionization.
(a) $0.5\ m\ Li2SO4$
(b) $0.5\ m\ KCl$
(c) $0.5\ m\ Al2(SO4)3$
(d) $0.1 m BaCl2.$

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Q 17Answer the following in detail.4 Marks

Which of the following solutions will have maximum boiling point elevation and which have minimum freezing point depression assuming the complete dissociation? (a) $0.1\ m\ KCl$ (b) $0.05\ m\ NaCl$ (c) $1\ m\ AlPO_4$ (d) $0.1\ m\ MgSO_4.$

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Q 18Answer the following in detail.4 Marks

A 0.15 m aqueous solution of KCl freezes at -0.510 °C. Calculate i and osmotic pressure at 0 °C. Assume volume of solution equal to that of water.

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Q 19Answer the following in detail.4 Marks

At $25 {}^\circ C$ a $0.1$ molal solution of $CH_3COOH$ is $1.35\%$ dissociated in an aqueous solution. Calculate freezing point and osmotic pressure of the solution assuming molality and molarity to be identical.

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Q 20Answer the following in detail.4 Marks

A mixture of benzene and toluene contains $30\%$ by mass of toluene. At $30{}^\circ C,$ vapour pressure of pure toluene is $36.7\ mm\ Hg$ and that of pure benzene is $118.2\ mm\ Hg.$ Assuming that the two liquids form ideal solutions, calculate the total pressure and partial pressure of each constituent above the solution at $30{}^\circ C.$

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Q 21Answer the following questions:1 Mark

Give an example of an ideal solution.

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Q 22Answer the following questions:1 Mark

State Raoult’s law for a solution containing a nonvolatile solute.

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Q 23Answer the following questions:1 Mark

Why naphthalene dissolves in benzene but not in water?

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