Question

acidity of normal rain water is due to
a) SO2
b) CO2
c) NO2
d) NO

Answer 1

By "normal" the question probably means unpolluted. Here it's useful to know that the oxides of nitrogen, often abbreviated NOx, are unstable and generally only form from the high-temperature reaction of N2 and O2 inside car engines. The sulfates are also readily removed from the air and typically generated by the combustion of sulfur impurities in coal, and also by the oxidation of sulfides in volcanic emissions. Finally, it's useful to recall that CO2 is always present in the atmosphere.

All of the oxides in the problem, being nonmetal oxides, can be expected to be acidic. But only one is ubiquitously present in the atmosphere naturally.

Answer 2

Lightning makes \(\text{NO}_x\)'s too

Answer 3

Quite right, thanks for the addition.