Q31 of 37 Page 1

Account for the following:

a) Moist SO2 decolourises KMnO4 solution


b) In general interhalogen compounds are more reactive than halogens (except fluorine).


(c) Ozone acts as as powerful oxidizing agent.


(a) When Sulphur dioxide is moist, it behaves as a reducing agent. It converts iron(III) ions to iron(II) ions and decolourises acidified potassium permanganate(VII) solution. The reaction is given as follows.


5SO2 + 2MnO4- + 2H2O → 5SO42- + 4H+ + 2Mn2+


This reaction is the basis of identification of the SO2 gas.


(b) When two different halogen compounds react with each other, interhalogen compounds are formed. For example, I2 + Cl2 (equimolar) → 2ICl. Interhalogen compounds are more reactive than halogens (except fluorine) because X–X’ bond in interhalogens is weaker than X–X bond in halogens except F–F bond, thus having low ionization enthalpy and higher reactivity.


(c) Ozone is an allotropic form of oxygen and exists as O3. Ozone is a powerful oxidizing agent because of the ease at which it liberates nascent oxygen.


O3 → O2 + O


This oxidizing power can be observed in an example: Ozone oxidises lead- sulphide to lead sulphate.


PbS(s) + 4O3(g) → PbSO4(s) + 4O2(g)


More from this chapter

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29

For the reaction A + B → products, the following initial rates were obtained at various given initial concentrations

Determine the half-life period.


OR


A first-order reaction is 50 % complete in 50 minutes at 300 K and the same reaction is again 50 % complete in 25 minutes at 350 K. Calculate activation energy of the reaction.


 30

Answer the following questions:

(a) Which of the following electrolytes is most effective for the coagulation of AgI/Ag+ sol?


- MgCl2, K2SO4, K4[Fe(CN)6]


(b) What happens when a freshly precipitated Fe(OH)3 is shaken with a little amount of dilute solution of FeCl3.


(c) Out of sulphur sol and proteins, which one forms macromolecular colloids?


 32

Identify the product formed when propan-1-ol is treated with Conc. H2SO4 at 413 K. Write the mechanism involved for the above reaction.

 33

(a) Give chemical tests to distinguish between the following pairs of compounds:

(i) Ethanal and Propanone.


(ii) Pentan-2-one and Pentan-3-one.(b) Arrange the following compounds in increasing order of their acid strength: Benzoic acid, 4- Nitrobenzoic acid, 3,4-Dinitrobenzoic acid, 4- Methoxybenzoic acid.


OR


Compare the reactivity of benzaldehyde and ethanal towards nucleophilic addition reactions. Write the cross aldol condensation product between benzaldehyde and ethanal.