Q: 58.5 g of NaCl and 180 g of glucose were separately dissolved in 1000 mL of water. Identify the correct statement regarding the elevation of boiling point of the resulting solution.

aligned 58.5 ~g NaCl & = 58.5 58.5 ~mol \\ & =1 ~mol \\ 180 ~g of glucose & = 180 180 =1 ~mol aligned Thus, we have 1 M NaCl and 1 M glucose solution. But NaCl dissociates in the solution and glucose does not dissociates. Thus particle concentration is more in NaCl . Hence, NaCl solution will have higher elevation in boiling point.

Q: A 0.5 molal solution of ethylene glycol in water is used as coolant in a car. If the freezing point constant of water be 1.86^ C per mole, the mixture shall freeze at

aligned & T_f=K_f m=1.86 0.5=0.93^ C ; \\ & T_f=-0.93^ C aligned

Question 1

A decimolar solution potassium ferrocyanide is 50 \% dissociated at 300 K . The osmotic pressure of solution is (R=8.314 JK ^ -1 ~mol ^ -1 )

Accepted Answer

=0.5 (50\% dissociated) The reaction involves is Total moles at equilibrium =1- +4 + Total =1+4 van't Hoff factor (i)= 1+4 1 =1+4 0.5=3 Osmotic pressure, =i C R T aligned C & =0.1 M =10^2 ~mol ~m ^ -3 \ & =3 10^2 8.314 300 \ & =7.483 10^5 Nm ^ -2 aligned or =7.48 ~atm

Question 2

58.5 g of NaCl and 180 g of glucose were separately dissolved in 1000 mL of water. Identify the correct statement regarding the elevation of boiling point of the resulting solution.

Accepted Answer

aligned 58.5 ~g NaCl & = 58.5 58.5 ~mol \ & =1 ~mol \ 180 ~g of glucose & = 180 180 =1 ~mol aligned Thus, we have 1 M NaCl and 1 M glucose solution. But NaCl dissociates in the solution and glucose does not dissociates. Thus particle concentration is more in NaCl . Hence, NaCl solution will have higher elevation in boiling point.

Question 3

One molar concentration of a solution represents :

Accepted Answer

1 M = 1 mole of solute in 1 L solution.

Question 4

Which of the following substances show the highest colligative properties?

Accepted Answer

Colligative property depends on the number of particles or ions. Option (d) consists 4 of ions due to which it shows highest colligative property.

Question 5

A 0.5 molal solution of ethylene glycol in water is used as coolant in a car. If the freezing point constant of water be 1.86^ C per mole, the mixture shall freeze at

Accepted Answer

aligned & T_f=K_f m=1.86 0.5=0.93^ C ; \ & T_f=-0.93^ C aligned

Question 6

How much ethyl alcohol must be added to 1 litre of water so that the solution will freeze at 14^ C ? ( K _ f . for water .=1.86^ C / mol )

Accepted Answer

7.5 ~mol T_f=K_f m T_f=K_f n_2 1000 w_1 14=1.86 n_2 1000 1000 n_2=7.5 ~mol

Question 7

Liquids A and B form an ideal solution in the entire composition range. At 350 ~K , the vapor pressures of pure A and pure B are 7 10^ 3 ~Pa and 12 10^ 3 ~Pa , respectively. The composition of the vap

Accepted Answer

P _ A ^ =7 10^ 3 P _ B ^ =12 10^ 3 x_ A ^ =0.4 ; x_ B ^ =1-0.4 x_ B ^ =0.6 P _ total = P _ A ^ ^ x_ A ^ + P _ B ^ x_ B ^ =7 10^ 3 0.4+12 10^ 3 0.6 =(7 0.4+12 0.6) 10^ 3 =10^ 4 x_ A = P _ A ^ ^ x^ A P _ total = 7 10^ 3 0.4 10^ 4 x_ A =0.28, x_ B =1-0.28=0.72

Question 8

The vapour pressure of two pure liquids A and B that form an ideal solution, are 400 and 800 ~mm of Hg respectivelyat a temperature t^ C . The mole fraction of A in a solution of A and B whose boiling

Accepted Answer

V.P. of solution at t^ C =760 ~mm [at b.p., V.P. of solution =atompheric pressure] Thus = P _ A ^ x _ A + P _ B ^ x _ B or P = P _ A ^ 0 x _ A + P _ B ^ 0 (1- x _ A ) [ x _ A + x _ B =1 ] or 760=400 X _ A +800 (1- X _ A )[ P =760 mmofHg ] or -800+760=-400 x_ A or -40=-400 x _ A or x_ A = 40 400 =0.1 Thus mole fraction in solution is 0.1

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