Name ______Date ______Period
HOMEWORK and TEST GRADE RECOVERY
for Chapter 7: Chemical Quantities
7.2 Molar Mass (Read pgs. 198 - 201in the chemistry textbook)
7.3 Calculations Using Molar Mass (Read pgs. 201 - 204 in the chemistry textbook)
1. (a) If you were to count out Avogadro's Number of water molecules, how many years would it take you
if you could count 100 molecules per second? Follow ALL math work rules!
(b) How many lifetimes is that if the average lifetime is 75 years? Follow ALL math work rules!
(c) So, now that we all (hopefully) agree that you don't have the time to count out a mole of anything,
how do scientists determine when they have a mole of an element or compound?
2. (a) What is a molar mass?
(b) What is the molar mass of the following elements?
(i) oxygen
(ii) platinum
(iii) uranium
3. What two things are represented by the formula subscripts of a chemical formula?
4. For each of the following 1) write the correct chemical formula if it is not given, and then 2) calculate the
molar mass of each - you do not have to show your work.
(a) iron (II) sulfate
(b) aluminum oxide
(c) C7H5NO3S, saccharin =
(d) C3H8O, rubbing alcohol =
(e) ammonium carbonate
(f) zinc acetate
5. (a) Calculate the molar mass of water. Round the atomic masses of the elements to 2 places past the
decimal point.
(b) Calculate the mass, in grams, of 3.52 moles of water. Follow ALL math work rules!
(c) How many water molecules are in 3.52 moles of water? Follow ALL math work rules!
(d) If the density of water is 1.0 g/ mL, prove mathematically whether or not you could go swimming in
3.52 moles of water. Do this by calculating how many gallons of water you would have. Follow
ALL math work rules!
6. One gel cap of an antacid contains 311 mg of calcium carbonate and 232 mg of magnesium carbonate. How
many moles of each substance are present in one gel cap? Follow ALL math work rules!
7. In the body, caffeine, which has a formula of C8H10N4O2, acts as a stimulant and a diuretic. How many
grams of nitrogen are in 2.50 g of caffeine? Follow ALL math work rules!
8. Calculate the mass, in grams, of each of the following: Follow ALL math work rules!
(a) 5.12 mol of Al
(b) 3.52 mol of magnesium bromide
(c) 0.75 mol of copper
8. Continued:
(d) 2.08 mol of ammonium sulfate
(e) 0.145 mole of ethanol, C2H5OH
9. Calculate the mass, in grams, in 2.28 mol of each of the following: Follow ALL math work rules!
(a) N2
(b) sodium oxide
(c) C6H14
(d) I2
9. Continued:
(e) calcium nitrate
10. Calculate the number of moles in each of the following: Follow ALL math work rules!
(a) 85.2 g of Ni
(b) 6.4 g of water
(c) 252.8 g of fructose, C6H12O6
(d) 144 g of potassium
(e) 308 g of barium sulfate
11. Calculate the number of moles in 4.00 g of each of the following: Follow ALL math work rules!
(a) gold
(b) chromium (III) hydroxide
(c) tin (IV) oxide
(d) vitamin C, C6H8O6
(e) calcium nitride
12. Calculate the number of atoms of N in each of the following: Follow ALL math work rules!
(a) 0.755 mole N2
(b) 0.82 g dinitrogen monoxide
(c) 40.0 g of sodium nitrate
(d) 6.24 x 1023 molecules of ammonia, NH3
(e) 1.4 x 1022 molecules of dinitrogen tetraoxide
13. Allyl sulfide, (C3H5)2S, is the substance that gives garlic, onions, and leeks their characteristic odor.
(a) How many moles of sulfur are in 23.2 g of allyl sulfide?
(b) How many atoms of hydrogen are in 0.75 mol of allyl sulfide?
(c) How many grams of carbon are in 4.20 x 1023 molecules of allyl sulfide?
(d) How many atoms of carbon are in 15.0 g of allyl sulfide?
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