Problem Set 1. Chemistry 1151, Fall 2008

PROBLEM SET 1. CHEMISTRY 1151, FALL 2008

Due: Tuesday, Sept 23, 5pm or earlier. These problems are to be turned in to your TA for grading. Put in your TA’s box with your name, TA’s name and section.

Work these problems on another sheet of paper. You may staple it to this sheet if you like. It is not necessary to rewrite the problem. You must show your work clearly and include units on your final answers. Each problem will be given a score of either 0, 1 or 2. Total possible score is 10.

1. The Morgan silver dollar has a mass of 26.73 g. By law, it was required to contain 90% silver, with the remainder being copper. a. When the coin was minted in the late 1800s, silver was worth $1.18 per troy ounce (31.3 g). At this price, what is the value of the silver in the silver dollar? b. Today, silver sells for $5.30 per troy ounce. How many Morgan silver dollars are required to obtain $25.00 worth of pure silver?

2. Write the chemical formulas for the following compounds: a. copper(I) oxide, b. potassium phosphate, c. sulfurous acid, d. zinc hydrogen carbonate, e. barium hydroxide, f. silver nitrate g. hydroselenic acid h. acetic acid

3. Determine the empirical and molecular formula of an organic compound containing only C and H given that combustion of a 1.50 g sample of the compound produces 4.71 g CO2 and 1.93 g H2O. The molecular mass of the compound is 28.0 g/mol.

4. Fermentation is a complex chemical process of wine making in which glucose is converted into ethanol and carbon dioxide: C6H12O6  2 C2H5OH + 2 CO2 glucose ethanol a. Starting with 525 grams of glucose, what is the maximum amount of ethanol in (a) grams, and (b) liters that can be obtained by this process? (density of ethanol = 0.789 g/L) b. If the mass of ethanol actually produced from 525 g of glucose is 205 grams, what is the % yield of the reaction?

5. Ag2S(s) + HNO3(aq)  AgNO3(aq) + H2S(aq) AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)

Consider the unbalanced equations above. Silver is often mined as the impure silver sulfide. A 5.00 g sample of impure Ag2S is heated with excess HNO3 and the H2S is completely removed from the solution during the heating. The solution is filtered to remove any unreacted solids. The filtrate is reacted with excess NaCl. The sample produces 0.430 g of AgCl. a. What is the mass percent of Ag2S in the sample? b. What is the mass percent of Ag in the sample?