CHE 11, Fall 1998
Quiz 3
September 25, 1998

Show your work for full credit. Give your answers with the correct number of significant figures.

1. The atomic mass of rhenium is 186.2. Given that 37.1% of natural rhenium is rhenium-185, what is the other stable isotope?

(a)

(b)

(c)

(d)

(e)

2. Adipic acid contains 49.32% C, 6.85% H, and 43.84% O by mass. What is the empirical formula for this compound?

3. Balance the following chemical equation.

Al₂(SO₄)₃ + Ca(OH)₂ Al(OH)₃ + CaSO₄

4. One of the major commercial uses of sulfuric acid is in the production of phosphoric acid and calcium sulfate (reaction shown below). The phosphoric acid is used for fertilizer. What mass of phosphoric acid could be formed from a mixture of 153.2 g calcium phosphate (MW = 310.3) and 256.5 g of sulfuric acid (MW = 98.08).

Ca₃(PO₄)₂ + 3 H₂SO₄ 3 CaSO₄ + 2 H₃PO₄

5. If the reaction described in question 4 yielded 75.3 g of phosphoric acid, what is the percent yield? (You will not be penalized on this question for incorrect answers on question 4.)