- (E) Chemical formulas involved in producing acid rain include: (i) H 2 O(l) +
CO2(g) H 2 CO3(aq) (ii) S(s) + O2(g) → SO2(g) The SO2(g) combines with
water to produce sulfurous acid: H 2 O(l) + SO2(g) H 2 SO3(g) Sulfur dioxide,
however, is not readily oxidized to sulfur trioxide in dry, clean air. Water
droplets and dust particles, however, catalyze the reaction between O 2 and
SO 2 in the air producing sulfur trioxide, SO 3 , which dissolves in water to
produce sulfuric acid, which is a much stronger acid: SO2(g) + O2(g) →
SO3(g) H 2 O(l) + SO3(g) → H 2 SO4(aq) This can cause considerable damage to
buildings, vegetation, and fish populations by destroying fish eggs.
(iii) Sources of NOx are more widespread. At temperatures over 2,370°F
(1,300°C), nitrogen combines with oxygen to form nitrogen monoxide: N2(g)
+ O2(g) → 2NO(g) These high temperatures can be achieved by: (i) the
internal-combustion engine; and (ii) lightning in the atmosphere. The
nitrogen monoxide slowly combines with oxygen to form soluble nitrogen
dioxide gas: 2NO(g) + O2(g) → 2NO2(g) Nitrogen dioxide readily dissolves in
water, producing a mixture of nitric and nitrous acids: 2NO2(g) + H 2 O(l) →
HNO3(aq) + HNO2(g) 85. (E) Between 1999 and the start of 2012 when the
world’s population increased from 6 billion to 7 billion people, the Asian
population, which represents 60% of the current world population, grew by
an estimated 579 million people making up about 57% of that increase. The
African population meanwhile contributed 28% to the population increase.
