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.