Question

5. Some areas of the nation have limestone in the soil and lake bottoms. Explain how the presence of this mineral acts as a natural buffer against acid rain.

Answer 1

Limestone is calcium carbonate Ca(Co3) it's dissociation equation is as follows: Ca(CO3) <----> Ca+2 + CO3-2 

but the solubility is very small in the presence of acid by LeChatlier's Principle you can shift to the right by adding acid 

H+ + CO3-2 <-----> H+CO3- (the bicarbonate ion which is really soluble) 

The system will pull more and more limestone out into solution as acid is added and neutralize the acid coming from the rain.