Work moles L2 2006.cwk

L2 Name ______________________________________ Page 1
Chemistry: Worksheet on Moles
1. Calculate the Formula Weight for the following: (* problems below use these formula wts)
ex. NaNO3 = Na + N + 3 x O = 23 + 14+ 3 (16) = 85 g
( add up the atomic weights)
a. Copper b. N c. O2 gas
d. H2O e. K2S f. Ca(NO3)2 (164 g)
g. Al2(SO4)3 (342 g) h. sodium oxide (62 g) i. calcium hydroxide (74 g)
1 Step conversions : Use these conversion factors to go between mol and:
Grams (or Mass) Particles (atoms, molecules Liters of gas at STP
or formula units)
formula weight in grams 6.02 x 10 23 atoms, etc 22.4 Liters
1 mol 1 mol 1 mol
2. How many mol are each of the following? (Change grams to mol)
ex. 42.5 g NaNO3 x ___1 mol___ = 0.500 mol NaNO3
85.0 g NaNO3
a. 42.0 g Carbon (3.50 mol) b. 112 g H2 gas (56.0 mol)
*c. 820 g Ca(NO3)2 (5.00 mol) *d. 86.0 g Al2(SO4)3 (0.252 mol)
*e. 6.20 g sodium oxide (0.100 mol) f. 93.5 grams magnesium fluoride (1.50 mol)

3. Find the mass of each of these mol : (change mol to grams) Page 2
ex. 0.75 mol NaNO3 x 85.0 g NaNO3 = 63.8 g NaNO3
1 mol
a. 0.600 mol F2 gas (22.8 g) b. 1.40 mol sulfur (44.8 g)
*c. 2.40 mol K2S (264 g) *d. 0.850 mol Al2(SO4)3 (291 g)
*e. 1.50 mol calcium hydroxide (111 g) f. 0.350 mol sodium phosphate (57.4 g)
4. How many mol are each of these volumes of gases at STP? (Change Liters at STP to mol)
ex. 11.2 L Ar x 1 mol Ar = 0.5 mol Ar (Don't need formula weights!)
22.4 L Ar
a. 39.2 L O2 (1.75 mol) b. 72.8 L Sulfur trioxide (3.25 mol)
5. Calculate the volume in Liters of each gas at STP. (Change mol to Liters at STP)
ex. 0.75 mol Ne x 22.4 L Ne = 16.8 L Ne (Don't need formula weights!)
1 mol
a. 0.600 mol O2 (13.4 L) b. 1.50 mol N2 (33.6 L)
6. How many mol are in these number of particles?(elements= atoms, molecular compounds =
molecules, ionic compounds = formula units)
(Change particles to mol, Don't need formula weights!)
ex. 3.01 x 10 22 atoms S x ___1 mol S_____ = 0.5 x 10 –1 mol S
6.02 x 10 23 atoms S
a. How many mol are 4.52 x 10 24 molecules H2O? (7.51 mol)
b. How many mol are 9.03 x 10 21 formula units K2S? (1.5 x 10 –2 mol)

L2 Moles : Name ___________________________________________________ Page 3
1. How many particles (atoms, molecules or formula units) are each of the following?
(Change mol to particles) (Don't need formula weights)
ex. 2 mol H2O x 6.02 x 10 23 molecules H2O = 12.04 x 10 23 molecules H2O
1 mol
a. How many molecules are in 0.350 mol CH4? (2.11 x10 23 )
b. How many formula units are in 1.30 mol Na2SO4? (7.83 x 10 23 )
2 Step conversions
For 2 step conversions, you need 2 of the conversion factors from the other side.
2. What is the mass in grams of these volumes of gases at STP? (Change Liters to grams)
ex. 11.2 L Ar x 1 mol Ar x 40 g Ar = 20 g Ar
22.4 L Ar 1 mol Ar (remember 1000 mL = 1 L)
a. 67.2 L Carbon dioxide (132 g) b. 224 mL N2O (0.440 g)
3. How many Liters at STP will the following mass of gases occupy? (Change grams to Liters)
a. 6.40 g SO2 (2.24 L) b. 42.0 g N2 (33.6 L)
ex for # 3. 27 g H2O x 1 mol x 6.02 x 10 23 molecules H2O = 9.03 x 10 23 molecules H2O
18 g H2O 1 mol H2O
3. How many atoms are in 30.0 g of Ar? (Change grams to particles) (4.52 x10 23 )
4. What is the mass in grams of 9.03 x 10 24 formula units FeCl2? (Change particles to grams)
(1902 g)
5. How many Liters at STP are 4.52 x10 23 molecules CO2 gas? (change particles to liters) (16.8 L)
6. How many molecules are in 16.8 L SO2 gas at STP? (change liters to Particles) (4.52 x 10 23 )

L2 Chemistry review problems: Moles and conversions Page 4
9. How many mol are each of the following?
a. 24.3 g ammonium sulfate (0.184 mol)
b. 4.48 L SO3 gas at STP (0.200 mol)
c. 2.11 x 10 21 atoms Carbon (3.50 x 10 –3 mol)
10. Find the mass in grams of 0.321 mol Aluminum hydroxide. (25.0 g)
11. What is the mass of 5.25 x 10 24 formula units Sodium sulfide? (680 g)
12. Calculate the mass of 1.68 L Krypton gas at STP. (6.29 g)
13. Calculate the volume in Liters of the following gases at STP.
a. 56.0 grams Carbon monoxide (44.8 L) b. 1.50 x 10 22 molecules O2 (0.558 L)
14. a. How many molecules are 42.0 g of Sulfur dioxide? (3.95 x 10 23 )
15. How many formula units are 5.00 x 10 –3 mol K2SO4? (3.01x 10 21 )
16. What is wrong with this statement: One mole of any two substances contains the same
number of atoms.