1. Review for Tomorrow’s Test MolesStoichiometry Percent composition Empirical Formula

2. Who is this famous Italian scientist, and what does his number represent?

3. He is Amadeo Avogadro His number: 6.022 x 10 23 There are 6.022 x 10 23 molecules of any substance in a mole of that substance

4. Define what a mole is: A mole of any substance is __ _________ ______ _________ __ _____.

5. A mole of any substance is its molecular weight expressed in grams

6. How much does one mole of H 2 SO 4 weigh?

7. H 2 SO 4 H 2 x 1.0 = 2.0 S 1 x 32.1 = 32.1 O 4 x 16.0 = 64.0 98.1 grams/mole

8. How many moles of NaCl are there in 14.65 g ?

9. Number of grams/mole: Na 1 x 23.0 = 23.0 Cl 1 x 35.5 = 35.5 58.5 g/mole Number of moles/ liter: 14.65 g x 1 mole = 0.25 moles 58.5 g

10. Write a balanced equation for the formation of salt (sodium chloride) from sodium metal and chlorine gas

11. 2 Na (s) + Cl 2 (g) 2 NaCl (s) (This is a combination or synthesis reaction)

12. How many grams are in 19.3 moles of AlCl 3 ?

13. 19.3 moles x 133.5 g = 2,576.6 g of AlCl 3 1 mole

14. How many moles are in 355.3 grams of Na 2 SO 4 ?

15. 355.3 g x 1 moles = 2.5 moles of Na 2 SO 4 142.1 g

16. How many grams does 1.807 x 10 24 molecules of water weigh?

17. How many grams does 1.807 x 10 24 molecules of water weigh? 1.807 x 10 24 molecules x 1 mole x 18.0g = 54.0 g 6.02 x 10 23 molecules 1 mole

18. How many molecules are in 112 grams of CH 4 ?

19. 112 g x 1 mole x 6.02 x 10 23 molecules = 4.214 x 10 24 16.0 g 1 mole molecules

20. Determine the percent composition of Each element in H 2 SO 4

21. Determine the percent composition of Each element in H 2 SO 4 H = 2 x 1.0 = 2.0 g S = 1 x 32.1 = 32.1 g O = 4 x 16.0 = 64.0 g 98.1 g/mole H = 2.0g x 100 = 2.0% 98.1g S = 32.1g x 100 = 32.7% 98.1g O = 64.0g x 100 = 65.2% 98.1g

22. An unknown compound is found to be 75% Carbon and 25% Hydrogen Determine it’s Empirical Formula (Use a 100 g sample )

23. An unknown compound is found to be 75% Carbon and 25% Hydrogen Determine it’s Empirical Formula (Use a 100 g sample ) If there is a 100.0 g sample, then 75.0 g of it is C and 25.0 g of it is H Carbon: 75.0 g x 1 mole = 6.25 moles 12.0 g Hydrogen: 25.0 g x 1 mole = 25.0 moles 1.0 g Find the ratio: 6.25 = 1 6.25 25.0 = 4 6.25 CH 4

24. HCl + Na 2 CO 3  CO 2 + H 2 O + NaCl How many grams of HCl and Na 2 CO 3 would you need to make 35.1 g of salt (NaCl)? 35.1 g = 0.6 moles of NaCl. Therefore 0.6 mole of HCl and 0.3 moles of Na 2 CO 3 are needed HCl needed: 0.6 moles x 36.5 g/mole = 21.9 g Na 2 CO 3 needed: 0.3 moles x 106 g/mole = 31.8 g

25. Balance this equation: Al (s) + O 2 (g) Al 2 O 3 (s)

26. Balanced ! 4Al (s) + 3 O 2 (g) 2Al 2 O 3 (s)

27. __Ca + __O 2 __CaO Balance the equation and determine the Molar Ratio needed between calcium and oxygen?

28. 2Ca + O 2 2CaO A 2 to 1 ratio between calcium & oxygen

29. Describe what is meant by a polyatomic ion

30. A group of atoms that bind together sharing an ionic charge and acting as one.

31. What is the sulfate radical and its valence charge?

32. Sulfate = SO 4 -2

33. What is a phosphate polyatomic ion and what is its valance charge when it forms a compound?

34. Phosphate = PO 4 -3