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Class 9 Chemistry Solutions


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Q21.4.675 gofacompoundwithempiricalformulaC3H3Oweredissolvedin212.5 gofpurebenzene.Thefreezingpointofsolutionwasfound1.02Clessthanthatofpurebenzene.Themolalfreezingpointconstantofbenzeneis5.1C.Calculate(i)therelativemolarmassand(ii)themolecularformulaofthecompound. \mathrm{Q} 21.4 .675 \mathrm{~g} of a compound with empirical formula \mathrm{C}_{3} \mathrm{H}_{3} \mathrm{O} were dissolved in 212.5 \mathrm{~g} of pure benzene. The freezing point of solution was found 1.02^{\circ} \mathrm{C} less than that of pure benzene. The molal freezing point constant of benzene is 5.1^{\circ} \mathrm{C} . Calculate (i) the relative molar mass and (ii) the molecular formula of the compound.

Q13. What is Raoults law. Give its three statements. How this law can help us to understand the ideality of a solution.
Q13. What is Raoults law. Give its three statements. How this law can help us to understand the ideality of a solution.

Q13.WhatisRaoultslaw.Giveitsthreestatements.Howthislawcanhelpustounderstandtheidealityofasolution.Q13. What is Raoults law. Give its three statements. How this law can help us to understand the ideality of a solution.

1. A solution contains 50 \mathrm{~g} of sugar dissolved in 450 \mathrm{~g} of water. What is concentration of this solution?
1. A solution contains  50 \mathrm{~g}  of sugar dissolved in  450 \mathrm{~g}  of water. What is concentration of this solution?

1.Asolutioncontains50 gofsugardissolvedin450 gofwater.Whatisconcentrationofthissolution?1. A solution contains 50 \mathrm{~g} of sugar dissolved in 450 \mathrm{~g} of water. What is concentration of this solution?

Worked Example 2: The pH of a solution is 9.63. Compute its hydrogen ion concentration.
Worked Example 2: The pH of a solution is 9.63. Compute its hydrogen ion concentration.

WorkedExample2:ThepHofasolutionis9.63.Computeitshydrogenionconcentration.Worked Example 2: The pH of a solution is 9.63. Compute its hydrogen ion concentration.

(c) Calculate the concentration of a solution in terms of molality which is obtained by mixing 250 \mathrm{~g} of 20 \% solution of \mathrm{NaCl} with 200 \mathrm{~g} of 40 \% solution of \mathrm{NaCl} .
(c) Calculate the concentration of a solution in terms of molality which is obtained by mixing  250 \mathrm{~g}  of  20 \%  solution of  \mathrm{NaCl}  with  200 \mathrm{~g}  of  40 \%  solution of  \mathrm{NaCl} .

(c)Calculatetheconcentrationofasolutionintermsofmolalitywhichisobtainedbymixing250 gof20%solutionofNaClwith200 gof40%solutionofNaCl.(c) Calculate the concentration of a solution in terms of molality which is obtained by mixing 250 \mathrm{~g} of 20 \% solution of \mathrm{NaCl} with 200 \mathrm{~g} of 40 \% solution of \mathrm{NaCl} .

Q 23. 3 g of a non-volatile non-electrolyte solute X are dissolved in 50 \mathrm{~g} of ether (molar mass = 74) at 293 \mathrm{~K} . The vapour pressure of ether falls from 442 torr to 426 torr under these conditions. Calculate the molar mass of solute X .(Ans: 122.6 \mathrm{~g} \mathrm{~mol}^{-1} )
Q 23. 3 g of a non-volatile non-electrolyte solute   X   are dissolved in  50 \mathrm{~g}  of ether (molar mass = 74) at  293 \mathrm{~K} . The vapour pressure of ether falls from 442 torr to 426 torr under these conditions. Calculate the molar mass of solute   X  .(Ans:  122.6 \mathrm{~g} \mathrm{~mol}^{-1}  )

Q23.3gofanonvolatilenonelectrolytesoluteXaredissolvedin50 gofether(molarmass=74)at293 K.Thevapourpressureofetherfallsfrom442torrto426torrundertheseconditions.CalculatethemolarmassofsoluteX.(Ans:122.6 g mol1)Q 23. 3 g of a non-volatile non-electrolyte solute X are dissolved in 50 \mathrm{~g} of ether (molar mass = 74) at 293 \mathrm{~K} . The vapour pressure of ether falls from 442 torr to 426 torr under these conditions. Calculate the molar mass of solute X .(Ans: 122.6 \mathrm{~g} \mathrm{~mol}^{-1} )

9. Tyndall effect is shown by:(a) sugar solution(b) paints(c) jelly(d) chalk solution
9. Tyndall effect is shown by:(a) sugar solution(b) paints(c) jelly(d) chalk solution

9.Tyndalleffectisshownby:(a)sugarsolution(b)paints(c)jelly(d)chalksolution9. Tyndall effect is shown by:(a) sugar solution(b) paints(c) jelly(d) chalk solution

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