Assertion (A): The pH of acid rain is less than 5.6. 
Reason (R): Carbon dioxide present in the atmosphere dissolves in rainwater and forms carbonic acid. 
(i) Both A and R are correct, and R is the correct explanation of A. 
(ii) Both A and R are correct, but R is not the correct explanation of A. 
(iii) Both A and R are not correct. 
(iv) A is not correct but R is correct. 

How many of these compounds will undergo disproportionation on hydrolysis? CO?, NO?, Cl?, F?, ClO?, Cl?O?, N?O?, SO?, P?O??

40. Best reducing agent is:
(a) He              (b) Be           (c) Li            (d) Al

37. Which element is considered to have oxidation number of +3 in all its compounds?

(a) Be              (b) Li             (c) Al         (d) Sc

36. Oxidation number ofS in S₂O₈^-2 is

(a) -2           (b) -6           (c) +2          (d) +6

32. Assertion: Na⁺ ion has an oxidation number of +1, Mg²⁺ ion, +2, Fe³⁺ ion, +3, Cl^– ion, –1, O^2– ion, –2; and so on.

Reason: For ions composed of only one atom, the oxidation number is equal to the charge on the ion.