2. The Mole Chapter 7 Chemical Quantities

3. Determine the percent composition of Fe(OH) 2 Fe – 1 x 55.8 = 55.8 O – 2 x 16 = 32 H – 2 x 1 = 2 Molar mass = 89.8

4. Divide element mass by molar mass, then multiply by 100. Fe –55.8 x 100 89.8 O – 32 x 100 89.8

5. Divide element mass by molar mass, then multiply by 100. H –2 x 100 89.8

6. Percent compositions % composition Fe = 62.1% % composition 0 = 35.6% % composition Fe = 2.2% Add them up. Do they total 100?

7. Empirical formulas Which of the following are empirical formulas? HCl K2C2O4K2C2O4 Pb 2 O 4

8. Empirical formulas Only one is an empirical formula. HCl The subscripts cannot be reduced.

9. Find the number of molecules in 24 g of CO 24 g (1 mole) ( 28 g ) = 0.86 moles of CO

10. Find the number of molecules in 24 g of CO 0.86 mol (6.02 x 10 23 ) (1 mol) 5.2 x 10 23 molecules of CO

11. Find the density of one mole of CO gas at STP. Density = Mass divided by volume D = 28 g = 1. 25 g/L 22.4 L

12. What is Avogadro’s number? 6.02 x 10 23 units of a substance

13. What is the difference between molecular mass and molar mass? Molecular mass is in atomic mass units; molar mass is in grams.

14. What is the difference between a 6 M solution of H 2 SO 4 and a 1 M solution of H 2 SO 4 ? The 6 M (molar) sulfuric acid is much stronger. It has 6 moles of the acid dissolved in 1 liter of solution. The 1 M has 1 mole dissolved in 1 liter.

15. Convert 872 g of ammonium oxide into moles. First find the correct formula for ammonium oxide. (NH 4 ) 2 O

16. Find the molar mass of ammonium oxide (NH 4 ) 2 O N – 2 x 14 = 28 H – 8 x 1 = 8 O – 1 x 16 = 16

17. Find the molar mass of ammonium oxide (NH 4 ) 2 O = 52 grams Set up a conversion factor to change from 872 g to moles.

18. Conversion factor 872 g ( 1 mol) 52 g = 16.8