Question

1. The atmospheric gas that forms a mild acid when dissolved in water is _____. (1 point)

Answer 1

The atmospheric gas that forms a mild acid when dissolved in water is carbon dioxide.  The inscription on a marble gravestone to become harder and harder to read over time is caused by chemical weathering. Biological evolution is NOT a factor that affects the rate of weathering in rocks.

Answer 2

The answers are;

1. Carbon dioxide
2. Chemical weathering
3. Biological Evolution

1. Carbon dioxide in the atmosphere mixes with rainwater for form carbonic acid;

CO2 + H2O  H2CO3 (a reversible reaction)

It is a weak acid because it dissociates partly in water with a pH of about 5.

2. Chemical weathering on the marble gravestone is due to rain. The rain is slightly acid because it has to dissolve carbon dioxide to form carbonic acid. The carbonic acid dissolves marble  (composed of largely calcium carbonate);

H2CO3 + CaCO3  Ca(HCO3)2 aq (CaHCO2 is soluble)

3. Biological evolution does not affect weathering of rock. Climate does. The higher the temperatures the rainfall, the higher the rate of weathering. Soft rocks like limestone are easily eroded by rainwater that rocks like quartz. The higher the surface area of rock exposed to these elements the higher their rate of weathering.