CLASS XII: ASSIGNMENT ON ALDEHYDES, KETONES, CARBOXYLIC ACIDS AND THEIR DERIVATIVES

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CLASS XII: ASSIGNMENT ON SOLUTIONS

SOLUTIONS

 

1 Mark Questions

1 How does the morality of a solution change with temperature?

2 What is the sum of the mole fractions of all the components in a three component system?

3 What temperature change is expected during the mixing of two liquids whose solution shows a negative deviation from Raoult’s law ?

4 What are interstitial solid solutions? Give an example.

5 What type of azeotrope is formed on mixing nitric acid and water?

2 Marks Questions

6 With the help of a suitable diagram, show that the lower vapour pressure of a solution than the pure solvent, causes a lowering of freezing point for the solution compared to that of pure solvent.

7 Concentrated nitric acid used in the laboratory work is 68% nitric acid by mass in aqueous is 1.504 g mL^-1?

8 Arrange the following aqueous solution, each of strength 0.1 M, in order of increasing freezing and boiling points. Justify your answer.

C₂H₅OH, Ba₃(PO₄)₂, Na₂SO₄, KCI, Li₃PO₄

3 Marks Questions

9 State Henry’s law for solubility of a gas in a liquid Explain the significance of Henry’s law constant (K_H), At the same temperature, hydrogen is more soluble in water than helium. Which of them will have a higher value of K_H and why ?

10 At 298 K, the vapour pressure of pure water is 23.75 mm Hg,

(a) At the same temperature, calculate the vapour pressure over 10% aqueous solution of an organic compound whose molecular weight is 60 g mol^-1?

(b) What will be the osmotic pressure of this solution at 298 K ? [R=0.082 L atm K^-1 mol^-1]

11 Two elements A and B form compounds having molecular formula AB₂ and AB_4. When dissolved in 20g of C₆H₆, 1g of AB₂ lowers the freezing point by 2.3 K, whereas 1.0g of AB₄ lowers it by 1.3 K. The molar depression constant for benzene is 5.1 K kg mol^-1. Calculate atomic mass of A and B.

5 Marks Questions

12 ( a ) What is meant by a ‘colligative property’?

      ( b ) Why does the presence of a solute in a solvent depress its freezing point?

      ( c ) The freezing point of pure nitrobenzene is 278.8 K. when 2.5 g of an unknown substance was dissolved in 100 g of nitrobenzene, the freezing point of solution was found to be 276.8 K. The freezing point depression constant of nitrobenzene is 8.0 K kg mol^-1. Calculate the molar mass of the unknown solute.

 

CLASS XII: ASSIGNMENT ON SURFACE CHEMISTRY

    SURFACE CHEMISTRY

 

1. Mark Questions

1. Write a mathematical expression showing relationship between the amount of solute absorbed per unit mass of the solid absorbent and the concentration of solute in the solution.
2. Why are lyophillic sols self-stabilized?
3. What is cause of Brownian move observed in colloidal solution?
4. Fill in the blanks:

1.    The enthalpy of chemisorptions is                                    then the enthalpy of physisorption.
2.  The liquid-liquid colloidal dispersion is called                              .

1. Indicate a chemical reaction involving a homogenous catalyst.

2. Mark Questions

 (F) What is Helmotlz electrical double layer? Define zeta potential.

  (G) Describe a chemical method each for the preparation of the sols of sulphur and platinum in water.

(H) To which colloidal system does milk belong? Name the dispersed phase and dispersion medium in milk.

 (I)

1. How is physically absorbed mass of a gas on a unit mass of absorbent related to pressure of the gas?

2. How do enzymes catalyse reaction? What role is played by co-enzymes?

 

       3. Marks Questions

(J) How are the colloidal classified on the bases of                                        the nature of interaction between dispersed phase and dispersion medium?  Describe an important characteristic of each class. Which of these sols need stabilizing agent for preservation?

       (K)

1. What are the two types of emulsions and how do they differ from one another? Give one example of each.
2. Which one among NaCI,, and  is most effective for the coagulation of Fe sol and why?

OR

1. Which will be absorbed more readily on the surface of charcoal and why? Or.
2.  In what way are multimolecular colloids different from macromolecular colloids? Give one example of each?
    
       

(l) Account for the following:

 1.  Ferric hydroxide sol coagulates on addition of a solution of potassium sulphate.

2.  The extent of physical adsorption decreases with the rises in temperature.

3.  A delta is formed at the point where the river enters the sea.

                                               Or

Define adsorption and write two important differences between physical adsorption and chemisorptions.

(M) What do you understand by activity and selectivity of catalyst? Describe some features of catalysis by zeolites.

CLASS XII : ASSIGNMENT ON ELECTRO CHEMISTRY

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