1. 1) How many moles of water are in an 82.3g sample?

2. 82.3g water
1mole water x = 1
18.02g water
4.57 mole water

3. 2) How many grams of oxygen are in a sample of gas that has a volume of 8.61L at STP?

4. 8.61L O2
1 mole O2
32g O2 x x = 1
22.4L O2
1 mole O2
12.3g O2

5. 3) How many liters of gas are contained in a sample that is made up of 42.48g of sulfur trioxide at STP?

6. 42.48g SO3
1 mole SO3
22.4L SO3 x x = 1
80.06g SO3
1 mole SO3
11.89L SO3

7. 4) How many formula units are present in a Iron (III) oxide sample that contains 1.68x1025 atoms

8. 1.68x1025 atoms
1 F.U. Fe2O3 x = 1
5 atoms
3.36x1024 F.U. Fe2O3

9. 5) How many atoms are present in a sample containing 1
5) How many atoms are present in a sample containing 1.96g of ammonium phosphate?

10. x = x x 1 20 atoms 1.58x1023 atoms 1.96g (NH4)3PO4 1 mole (NH4)3PO4
6.02x1023F.U. (NH4)3PO4 x x 1
149.12g (NH4)3PO4
1 mole (NH4)3PO4
20 atoms x =
1.58x1023 atoms
1 F.U. (NH4)3PO4

11. 6) How many liters of gas at STP are contained in a sample of chlorine that contains 3.2x1011 atoms?

12. x = x x 1 6.0x10-12L Cl2 22.4L Cl2 1 mole Cl2 3.2x1011 atoms Cl
1 molecule of Cl2
1 mole Cl2 x x 1
2 atoms Cl
6.02x1023 molecules Cl2
22.4L Cl2 x =
6.0x10-12L Cl2
1 mole Cl2

13. 7) How many atoms of oxygen are contained in a 53
7) How many atoms of oxygen are contained in a 53.82g sample of aluminum sulfate?

14. x = x x 1 12 atoms O 1.136x1024 atoms O 53.82g Al2(SO4)3
1 mole Al2(SO4)3
6.02x1023F.U. Al2(SO4)3 x x 1
342.14g Al2(SO4)3
1 mole Al2(SO4)3
12 atoms O x =
1.136x1024 atoms O
1 F.U. Al2(SO4)3

15. 8) How many formula units of hydrochloric acid are present in a 75
8) How many formula units of hydrochloric acid are present in a 75.0mL solution if it has a concentration of 0.258M?

16. x = x x 1 0.258moles HCl 1.16x1022 F.U. HCl 75.0mL HCl Soln.
1 mole HCl

17. 9) What is the length of a copper wire (cylinder) that has a diameter of cm and contains 4.91x1022 copper atoms? Vcyl=πr2h, Dcu = 8.96g/mL

18. x = x x 1 h = 1840cm 1 mole Cu 0.5785 cm3 Vcyl=πr2h
4.91x1022atoms Cu x
1 mole Cu x
63.55g Cu 1
1 mole Cu
6.02x1023atoms Cu
1 cm3Cu x =
cm3
8.96g Cu
Vcyl=πr2h
0.5785cm3 = 3.14(0.0100cm)2h
h = 1840cm

19. Answers 1) 4.57 mole water 2) 12.3g O2 3) 11.89L SO3
4) 3.36x1024 F.U. Fe2O3
5) 1.58x1023 atoms
6) 6.0x10-12L Cl2
7) 1.136x1024 atoms O
8) 1.16x1022 F.U. HCl
9) 1840cm