Depression in Freezing Point

Q.

QUESTION 2.20

A $5\%$ solution (by mass) of cane sugar in water has freezing point 271 K. Calculate freezing point of $5\%$ glucose in water if freezing point of pure water is 273.15K.

Q.

The value of observed and calculated molecular weight of silver nitrate are 92.64 and 170 respectively. The degree of dissociation of AgNO₃ will be:

1. 46.7%

2. 60.23%

3. 60%

4. 83.5%

Q.

What is meant by Equivalent weight give me a simple formula to understand it?

Q. Solution of oxalic acid is prepared by dissolving 0.63g of acid in 250ml of solution .calculate molarity

Q.

Question 2.32

Calculate the depression in the freezing point of water when 10g of $C{H}_{3}C{H}_{2}CHClCOOH$ is added to 250 g of water, $K_a=1.4\times {10}^{-3}$; $K_f=1.86Kkgmo{l}^{-1}$

Q.

A solute A dimerizes in water. The boiling point of a $2$ molal solution of A is $100.52°\mathrm{C}$. The percentage association of A is (round off to the nearest integer) (use ${\mathrm{K}}_{\mathrm{b}}$ for water $=0.52\mathrm{K}\mathrm{kg}{\mathrm{mol}}^{-1}$; boiling point of water $=100°\mathrm{C}$) -

Q. 12.976g of lead combines with 2.004g of oxygen to form PbO2. PbO2 can also be produced by heating lead nitrate and it was found that the pecentage of oxygen present in PbO2 is 13.38% with the help of given information illustrate the law of constant composition.

Q.

If molality of the dilute solution is doubled, the value of molal depression constant $\left(K_f\right)$ will be

1. Halved

2. Unchanged

3. Tripled

4. Doubled

Q.

QUESTION 2.31

The depression in freezing point of water observed for the same amount of acetic acid, triehloroacetie acid and trifluoroacctie acid increases in the order given above. Explain briefly.

Q. Henrys constant for Argon is 40K bar in water. Determine molal concentration of Argon in water when it is stored above water at 10 bar pressure.

Q.

What is the effect of temperature on the solubility of a solid in liquid.

Q.

What is depression of freezing point?

Q. If relative decrease in vapour pressure is 0.4 for a solution containg 1 mol of nacl in 3 mol of water then % ionization Of nacl is

Q. What is mass of sodium acetate required to make 200 ml of 0.245 molar aqueous solution?

Q. A solution of urea in water has a boiling point of ${100.18}^{\circ }C.$ Calculate the freezing point of the same solution. Molal depression and elevation constants for water $K_f$ and $K_b$ are ${1.86}^{\circ }Ckgmo{l}^{-1}$ and ${0.512}^{\circ }Ckgmo{l}^{-1}$ respectively.

1. $-{0.654}^{\circ }C$
2. $-{0.98}^{\circ }C$
3. $-{1.54}^{\circ }C$
4. $+{0.101}^{\circ }C$

Q. if pA and pB are 108 and 36 torr respectively what will be the mole fraction of A is vapour phase if B has mole fraction in solution is 0.5 1. 0.25 2. 0.75 3. 0.60 4. 0.3

Q. Which of the following has been arranged in order of decreasing freezing point?

1. $0.05\text{M}KN{O}_3>0.04\text{M}CaC{l}_2>0.14\text{M}\text{sugar}>0.075\text{M}CuS{O}_4$
2. $0.04\text{M}BaC{l}_2>0.14\text{M}\text{sucrose}>0.075\text{M}CuS{O}_4>0.05\text{M}KN{O}_3$
3. $0.075MCuS{O}_4>0.14M\text{sucrose}>0.04MBaC{l}_2>0.05MKN{O}_3$
4. $0.075\text{M}CuS{O}_4>0.05\text{M}NaN{O}_3>0.14\text{M}\text{sucrose}>0.04\text{M}BaC{l}_2$

Q.

Benzoic acid dissolved in benzene shows a molecular mass of _______ g/mol.

1. 122

2. 244

3. 366

4. 488

Q. 28. density of 2 molal sucrose solution is 1.4 gram/ml at 25 degree centigrade temperature then find out osmotic pressure

Q. vant Hoff factor for aqueous Na2SO4 solution with degree of ionisation α = 0.75, is

Q.

The van't Hoff factor "i" for 0.2 molal aqueous solution of urea is:

1. 0.2

2. 0.1

3. 1.2

4. 1.0

Q. $20\text{g}$ of non-electrolyte, non-volatile solute $\left(C_x{H}_{2x}{O}_x\right)$ when dissolved in $100\text{g}$ water at ${100}^{\circ }\text{C}$, lowers the vapour pressure of solution by $\left(\frac{1}{100}\right)th$ of the vapour pressure of pure water. What is formula of the compound?

1. $C_6{H}_{12}{O}_6$
2. $C_{12}{H}_{24}{O}_{12}$
3. $C_{44}{H}_{88}{O}_{44}$
4. $C_3{H}_6{O}_3$

Q.

${\mathrm{AB}}_2$ is $10\%$ dissociated in water to $A^{2+}$ and $B^{-}$. The boiling point of a $10.0$ molal aqueous solution of $A{B}_2$ is ____________ $°C$. (Round off to the Nearest Integer).

[Given: Molal elevation constant of water $K_b=0.5Kkgmo{l}^{-1}$ boiling point of pure water $=100°C$].

Q. The amount of urea to be dissolved in $500cc$ of water $(K_f={1.86}^{\circ }Ckgmo{l}^{-1})$ to produce a depression of ${0.186}^{\circ }C$ in the freezing point is:
( Molar mass of urea = $60g/mol$)

1. $9$
2. $6g$
3. $3g$
4. $0.5g$

Q.

Molecules of benzoic acid ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}$ dimerises in benzene.$‘\mathrm{W}’\mathrm{g}$ of the acid dissolved in $30\mathrm{g}$ of benzene shows a depression in freezing point equal to $2\mathrm{K}$. If the percentage association of the acid to form a dimer in solution is$80$, then w is:

(Given that ${\mathrm{K}}_{\mathrm{f}}=5\mathrm{K}\mathrm{kg}{\mathrm{mol}}^{-1}$, Molar mass of benzoic acid$=122\mathrm{g}{\mathrm{mol}}^{-1}$)

Q.

Question 53
Assertion (A) When NaCl is added to water a depression in freezing point is observed.
Reason (R) The Lowering of vapour pressure of a solution causes depression in the freezing point.

Q. During depression in the freezing point in a solution, the following are in equilibrium.

1. Liquid solvent, solid solvent
2. Liquid solvent, solid solute
3. Liquid solute, solid solute
4. Liquid solute, solid solvent

Q.

The freezing point of a solution prepared from 1.25 gm of a non-electrolyte and 20gm of water is 271.9 K. If molar depression constant is 1.86 K mole^-1, then molar mass of the solute will be

1. 105.7

2. 106.7

3. 93.9

4. 115.3

Q. Sodium chloride or calcium chloride is used to clear snow from the roads. This is because:

1. $NaCl$ increases the freezing point of water
2. $NaCl$ decreases the freezing point of water
3. $NaCl$ decreases the boiling point of water
4. $NaCl$ lowers the vapour pressure of water

Q.

Which among the following will show maximum osmotic pressure?

(A) 1M Nacl

(B) 1M Mgcl₂

(C) 1M (NH₄)₃PO₄

(D) 1M Na₂SO₄

Please specify the reasons