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

2. 82.3g water 1 x 1mole water 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 O 2 1 x 1 mole O 2 22.4L O 2 x 32g O 2 1 mole O 2 = 12.3g O 2

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 SO 3 1 x 1 mole SO 3 80.06g SO 3 x 22.4L SO 3 1 mole SO 3 = 11.89L SO 3

7. 4) How many formula units are present in a Iron (III) oxide sample that contains 1.68x10 25 atoms

8. 1.68x10 25 atoms 1 x 1 F.U. Fe 2 O 3 5 atoms = 3.36x10 24 F.U. Fe 2 O 3

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

10. 1.96g (NH 4 ) 3 PO 4 1 x 1 mole (NH 4 ) 3 PO 4 149.12g (NH 4 ) 3 PO 4 x 6.02x10 23 F.U. (NH 4 ) 3 PO 4 1 mole (NH 4 ) 3 PO 4 1.58x10 23 atoms x 20 atoms 1 F.U. (NH 4 ) 3 PO 4 =

11. 6) How many liters of gas are contained in a sample of chlorine that contains 3.2x10 11 atoms?

12. 3.2x10 11 atoms Cl 1 x 1 molecule of Cl 2 2 atoms Cl x 6.02x10 23 molecules Cl 2 1 mole Cl 2 6.0x10 -12 L Cl 2 x 22.4L Cl 2 1 mole Cl 2 =

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

14. 53.82g Al 2 (SO 4 ) 3 1 x 1 mole Al 2 (SO 4 ) 3 342.14g Al 2 (SO 4 ) 3 x 6.02x10 23 F.U. Al 2 (SO 4 ) 3 1 mole Al 2 (SO 4 ) 3 1.136x10 24 atoms O x 12 atoms O 1 F.U. Al 2 (SO 4 ) 3 =

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

16. 75.0mL HCl Soln. 1 x 1L HCl Soln. 1000mL HCl Soln. x 1L HCl Soln. 1.16x10 22 F.U. HCl x 0.258moles HCl 1 mole HCl = 6.02x10 23 F.U. HCl

17. 9) What is the length of a copper wire (cylinder) that has a diameter of 0.0200cm and contains 4.91x10 22 copper atoms? V cyl =πr 2 h, D cu = 8.96g/mL

18. 4.91x10 22 atoms Cu 1 x 63.55g Cu 1 cm 3 Cu x 8.96g Cu 0.5785 cm 3 x 1 mole Cu = 6.02x10 23 atoms Cu V cyl =πr 2 h0.5785cm 3 = 3.14(0.0100cm) 2 h h = 1840cm

19. Answers 1) 4.57 mole water 2) 12.3g O 2 3) 11.89L SO 3 4) 3.36x10 24 F.U. Fe 2 O 3 5) 1.58x10 23 atoms 6) 6.0x10 -12 L Cl 2 7) 1.136x10 24 atoms O 8) 1.16x10 22 F.U. HCl 9) 1840cm