Surface Chemistry (Questions)

A.    Very-Short-Answer Questions

1.      Why do atoms at a surface show properties that are different from those of atoms in the bulk?

2.      How can the surface area of a solid body be increased?

3.      All the atoms in a solid particle do not have the same energy. Which atoms have a higher energy than the others?

4.      In what different ways can a system minimize its surface energy?

5.      Why is a substance a better adsorbent when it is in form of a fine powder than in the form of coarse particles?

6.      Why is adsorption disfavored by a rise in temperature?

7.      Why does the pH of an aqueous solution of acetic acid increase when animal charcoal is added to it?

8.      What is negative adsorption?

9.      Name three common adsorbents.

10.  What is activated charcoal?

11.  What is an adsorption isotherm?

12.  Is adsorption an exothermic process or an endothermic one?

13.  What are colloids?

14.  Is a colloidal system homogeneous or heterogeneous?

15.  Identify the dispersed phase and the dispersion medium in

(i)emulsion      (ii)foam           (iii)gel              (iii)sol              (v)hydrosol

16.  What type of colloids are the following?

(i) Tea              (ii) butter         (iii) milk                       (iv) fog                         (v) cloud         

(vi) ink             (vii) smoke      (viii) gem stones         (ix) toothpaste             (x) soap lather

17.  How does a surfactant like sodium stearate, CH₃(CH₂)₁₆ COO^-Na⁺ , orient itself at the water/air interface and at the benzene/air interface?

18.  What is critical micelle concentration (CMC)?

19.   Name a (i) nonionic, (ii) cationic and (iii) anionic surfactant that can form micelles.

20.  Why do colloidal sols appear turbid?

21.  What is the origin of electrical charge on colloidal particles?

22.  Three test tubes A, B and C all contain gold sol but their colors are yellow, blue and violet respectively. Why are their colors different?

23.  How can colloidal particles be separated from molecules and ions in solution?

24.  What is Brownian motion?

25.  How can colloidal particles not settle at the bottom of the dispersion medium under gravity?

26.  Why is NH₃ more readily adsorbed on an adsorbent than CO₂ is?

27.  Which of the following electrolytes will be the most effective in the coagulation of AgIIAg⁺ colloids?

                        NaCI, K₂SO₄, FeCI₃, K₄[Fe(CN)₆]

28.  What is peptization?

29.  What is dialysis?

30.  A gold sol is precipitated when NaCI is added to it but a gelatin sol is not. Why?

31.  What is gold number?

32.  Which of the following will be the most effective in precipitating a ferric oxide sol?

                                         KCI, BaCI₂, Na₂SO₄

33.  Which type of an emulsion is milk-oil-in-water or water-in-oil?

34.  In what ways can a colloidal system be destroyed?

35.  What is a catalyst?

36.  What are homogeneous and heterogeneous catalyst?

37.  What is a catalytic converter in motor vehicles?

38.  Can a catalyst initiate a reaction?

39.  The reaction 2SO₂(g) + O₂ → 2SO₃(g) may be catalyzed by platinum, Fe₂O₃ or V₂O₅. Which of these catalysts gives the best yield of product at a certain temperature?

40.  What is catalytic poisoning?

41.  What is an enzyme?

42.  What is the effect of temperature on enzymic activity?

43.  Why do enzymes show specificity in catalyzing a reaction?

44.  What are competitive and noncompetitive inhibitors of enzyme-catalysed reactions?

45.  How does the rate of an enzyme-catalysed reaction with

(i) increase in the concentration of enzyme and

(ii) increase in the concentration of the substrate?

46.  What is the effect of pH on enzyme-catalysed reaction?

47.  How is rubber obtained from latex?

48.  Why do deltas form at the mouths of river?

49.  What is Cottrell precipitator?

B.    Short Answer Questions

1.   What is adsorption? How does it differ from absorption?

2.   What is the Freundlich isotherm for (i) the adsorption of gases and (ii) the adsorption of solutes from solution?

3.   In gravimetric estimation why precipitations generally carried out after heating the solution?

4.   What is physisorption? How does it differ from chemisorption?

5.   How are colloids classified?

6.   What are lyophilic and lyophobic colloids?

7.   What are micelles?

8.    What is the Tyndall effect?

9.   What is an ultramicroscope?

10.  What is Hardy-Schulze rule?

11.  Mention the different methods of determining whether an emulsion is the O/W or W/O type.

12.  What is a protective colloid?

13.  What are emulsifiers? How do they stabilize an emulsion?

14.  How does a heterogeneous catalyst work?

15.  What is a shape-selective catalyst?

16.  What is the lock-and-key model of enzyme activity?

17.  Explain the cleansing action of soaps and detergents.

18.  Explain the Bosch-Haber synthesis of NH₃ on an iron surface?

C.    Long-Answer Question

  1. What are the characteristics of physisorption?

   2. What is chemisorption? What are the characteristics?

   3.What are the characteristics of catalysis?

   4. Write a note on the applications of the adsorption?

   5.  In what different ways colloids be prepared?

   6. What are zeolites? How do they function as shape-selective catalyst? Explain giving examples.

   7.What is the difference between multi-molecular and macro-molecular colloids? Give one example of each. How are associated colloids different from these type of colloids?