Due date: 22/03/2011
Average Atomic Mass Problems
1. What is average atomic mass of Lithium if 7.42% exists as 6Li (6.015 g/mol) and 92.58% exists as 7Li (7.016 g/mol)?
2. Magnesium has three naturally occuring isotopes. 78.70% of Magnesium atoms exist as Magnesium-24 (23.9850 g/mol), 10.03% exist as Magnesium-25 (24.9858 g/mol) and 11.17% exist as Magnesium-26 (25.9826 g/mol). What is the average atomic mass of Magnesium?
3. Neon has two major isotopes, Neon-20 and Neon-22. Out of every 250 neon atoms, 225 will be Neon-20 (19.992 g/mol), and 25 will be Neon-22 (21.991 g/mol). What is the average atomic mass of Neon?
4. What is the atomic mass of Hafnium if out of every 200 atoms, 10 have mass 176.00 g/mol, 38 have mass 177.00 g/mol, 54 have mass 178.00 g/mol, 28 have mass 179.00 g/mol, and 70 have mass 180.00 g/mol?
5. In a sample of 200 Chlorine atoms, it is found that 151 are 35Cl (34.969 g/mol), and 49 are 37Cl (36.966 g/mol). What is the average atomic mass of Chlorine?
6. Without doing any math, are there more Bromine-79 atoms or more Bromine-80 atoms on earth? (Hint: look at the periodic table.)
1a) How many moles of chlorine gas (Cl2) would react with 5 moles of sodium (Na) according
to the following chemical equation? (Balance equation.)
Na + Cl2 --> NaCl
1b) Using the equation (after it is balanced) above, determine the amount of product that can be
produced from 24.7 g Na.
1c) How many molecules of product would be produced from 24.7g Na?
2a) In the reaction 2C8H18 + 25O2 --> 16CO2 + 18 H2O, the ratio of volumes of O2 to CO2
2b) If 27.3g of C8H18 are combusted, what mass of water will be produced?
2c) How many molecules of CO2 will be produced?
2d) How many atoms of H are in 2 mol of C8H18?
2e) What is the percentage, by mass, of the H in 2 mol of C8H18?
Limiting Reagent Worksheet
All of the questions on this worksheet involve the following reaction: When copper (II) chloride reacts with sodium nitrate, copper (II) nitrate and sodium chloride are formed.
1)Write the balanced equation for the reaction given above:
2)If 15 grams of copper (II) chloride react with 20 grams of sodium nitrate, how much sodium chloride can be formed?
3)What is the limiting reagent for the reaction in problem #2? ______
4)How much of the nonlimiting reagent is left over in this reaction?
5)If 11.3 grams of sodium chloride are formed in the reaction described in problem #2, what is the percent yield of this reaction?
Molarity Practice Problems
1)How many grams of potassium carbonate are needed to make 200 mL of a 2.5 M solution?
2)How many liters of 4 M solution can be made using 100 grams of lithium bromide?
3)What is the concentration of a 450 mL solution that contains 200 grams of iron (II) chloride?
4)How many grams of ammonium sulfate are needed to make a 0.25 M solution at a concentration of 6 M?
5)What is the concentration of a solution that has a volume of 2.5 L and contains 660 grams of calcium phosphate?
6)How many grams of copper (II) fluoride are needed to make 6.7 liters of a 1.2 M solution?
7)How many liters of 0.88 M solution can be made with 25.5 grams of lithium fluoride?
8)What is the concentration of a solution that with a volume of 660 that contains 33.4 grams of aluminum acetate?
9)How many liters of 0.75 M solution can be made using 75 grams of lead (II) oxide?
10)How many grams of manganese (IV) oxide are needed to make a 5.6 liters of a 2.1 M solution?
11)What is the concentration of a solution with a volume of 9 mL that contains 2 grams of iron (III) hydroxide?
12)How many liters of 3.4 M solution can be made using 78 grams of isopropanol (C3H8O)?
13) What is the concentration of a solution with a volume of 3.3 mL that contains 12 grams of ammonium sulfite?
1)If I have 340 mL of a 0.5 M NaBr solution, what will the concentration be if I add 560 mL more water to it?
2)If I dilute 250 mL of 0.10 M lithium acetate solution to a volume of 750 mL, what will the concentration of this solution be?
3)If I leave 750 mL of 0.50 M sodium chloride solution uncovered on a windowsill and 150 mL of the solvent evaporates, what will the new concentration of the sodium chloride solution be?
4)To what volume would I need to add water to the evaporated solution in problem 3 to get a solution with a concentration of 0.25 M?