Passage II
When fossil fuels are burned, sulfur (S) enters the air as sulfur dioxide gas (SO2), which is then converted to sulfuric acid (H2SO4) :
1) 2SO2 + O2 →2 SO3
2) SO3 + H2O → H2SO4
Rain containing the H2SO4 then deposits the sulfur into lakes.
Figure 1 shows data on the average rate of sulfur deposition in numerous lakes throughout Ontario, Canada. Figure 2 shows, for Zones 1-5 in Figure 1, the average SO42- concentration (which is a measure of deposited H2SO4), the average alkalinity (the average concentration of substances in lake water that neutralize acidity), and the average pH in lake waters versus the average rate of sulfur deposition.
Figures adapted from B. P. Neary and P. J. Dillon, "Effects of Sulfur Deposition on Lake-Water Chemistry in Ontario, Canada." ©1988 by Macmillan Journals, Ltd.
6. Based on the data in Figure 2, as the average rate of sulfur deposition increased, the average lake water pH:
Your Answer is
Correct Answer is H
Explanation
It can be seen from Figure 1 that from Zone 1 to Zone 5, the sulfur deposition increases sequentially; while Figure 2 shows that from Zone 1 to Zone 5, the pH decreases sequentially. So as the sulfur deposition increases, the pH should decrease.