1. A sandwich is made up of two slices of bread, two slices of chicken, and one slice of tomato. What are the mass percentages of bread, chicken, and tomato in the sandwich? (28 g/slice bread, 35 g/slice chicken, 49 g/slice tomato). 32% bread, 40% chicken, 28% tomato
2. The sandwich in problem 1 contains 18 g protein, 5 g fat, 37 g carbohydrate, and the remainder is moisture (H2O). What are the mass percentages of protein, fat, carbohydrate, and moisture in the sandwich? 10.% protein, 2.9% fat, 21% carbohydrate, 66% moisture
3. Concentrated nitric acid is 70% HNO3 (the other 30% is water). What mass of concentrated nitric acid must be taken to obtain 125 g of HNO3? 179 g
4. Concentrated sulfuric acid is 96% H2SO4 and has a density of 1.86 g/mL. What mass of H2SO4 is contained in 5.00 x 102 mL of the concentrated acid? 893 g
5. Calculate the mass percentages of C, H, and Cl for each molecule in Section 7, Problem 8.
(a) C3H7Cl: 45.88% C, 8.98% H, 45.14% Cl
(b) C4H6Cl2: 38.44% C, 4.84% H, 56.73% Cl
(c) C7H7Cl: 66.42% C, 5.57% H, 28.01% Cl
(d) C4H9Cl: C 51.90% C, 9.80% H, 38.30% Cl
6. Calculate the mass percentages of of Ca, S, O, H, SO42-, and H2O in CaSO4.2H2O.
Molar mass of CaSO4.2H2O = 172.17 g/mol
2.34% H, 55.76% O, 18.62% S, 23.28% Ca, 55.79% SO42-, 20.93% H2O
7. Calculate the mass percentages of Fe, N, H, S, O, NH4+, SO42-, and H2O in iron(II) ammonium sulfate hexahydrate (Fe(NH4)2(SO4)2.6H2O, also called ferrous ammonium sulfate).
Molar mass of (Fe(NH4)2(SO4)2.6H2O: 392.13 g/mol
5.14% H, 7.14% N, 57.12% O, 16.35% S, 14.24% Fe, 9.20% NH4+, 48.99% SO42-, 27.56% H2O
8. A student crosses the border and the customs officer seizes a bag of white powder. The student says it is fertilizer for her violets (urea; formula CH4N2O). The customs officer thinks it is heroin (formula C21H23NO5). Analysis shows the compound to have 20.0% C, 6.7% H. Which is the powder most likely to be: urea or heroin?
Urea contains 6.71% H, 20.00% C, heroin contains 6.28% H, 68.28% C. Thus, the white powder is urea.
This page is
http://chemiris.labs.brocku.ca/~chemweb/courses/chem180/Study_Guide_Ans_Pt8.html
Created October 1, 2000 by M. F. Richardson
© Brock University, 2000