« on: November 28, 2007, 10:12:14 AM »
This is the stimulus with two questions.
Oxygen-18 is heavier-than-normal isotope of oxygen. In a rain cloud, water molecules containing oxygen-18 are rarer than water molecules containing normal oxygen. But in rainfall, a higher proportion of all water molecules containing oxygen-18 than of all water molecules containing ordinary oxygen descends on earth. Consequently, scientists ordinary oxygen descends to earth. Consequently, scientists were surprised when measurements along the entire route of rain clouds' passage frm the Atlantic Ocean, the site of their original formation, across the Amazon forests, where it rains almost daily, showed that the oxygen-18 content of each clouds remained fairly constant.
Which of the following statements, if true, best helps to resolve the conflict between scientists' expectations, based on the known behavior of oxygen-18, and the result of their measurements of the rain clouds' oxygen-18 content.
Having took a nice load of chem and organic helped to get to the right answer, but I am not so sure I KNOW WHY it's correct.
b) Like the oceans, tropical rain forests can create or replenish rain clouds in the atmosphere above them.
Which of the following inferences about an individual rain cloud is supported by the passage?
Stuck between these two:
a) Once it is formed over the Atlantic, the rain cloud contains more ordinary oxygen than oxygen-18.
c) The cloud's rainfall contains more oxygen-18 than ordinary oxygen.
correct answer highlight here---->A