35. A problem of global concern is acid deposition, more commonly referred to as acid rain. Some acidity in rainwater is normal due to the dissolving of atmospheric carbon dioxide, but the minimum pH value that can be attributed to this is 5.6. Much lower pH values have been measured in rain and snow in many parts of the world. This drop in pH is primarily caused by the burning of fossil fuels, which releases oxides of sulphur and nitrogen into the atmosphere. Coal is composed mainly of carbon. The thermochemical equation that correctly represents the complete combustion of carbon is A. C(s)+O2(g)CO2(g)H=+393.5kJ B. C(s)+O2(g)CO2(g)H=393.5kJ C. 2C(s)+O2(g)2CO(g)H=221.0kJ D. 2C(s)+O2(g)2CO(g)H=+221.0kJ B C D