1. Chapter 9 Chemical Quantities

2. (gramsA  molsA )  (molsB  gramsB )
Here I give you mass of one you tell me mass of the other
key? start and end w/ grams; but must cross thru mol bridge!!!
Basic method?
(gramsA  molsA )  (molsB  gramsB )

4. example
How many grams of oxygen gas are required to completely react with 14.6 g of solid sodium to form sodium oxide, Na2O?

5. 4Na O2  2Na2O g
14.6 g
mol Na
mol O2
notice that there are always non-players. but they are needed for balancing the equation!

6. example cont’d mol bridge
remember: they can only talk mol language from the balanced equation!
14.6 g Na
1 mol Na
1 mol O2
32.0 g O2
23.0 g Na
4 mol Na
1 mol O2
mol bridge
= 5.08 g O2

7. example
When 20.4 grams of sodium metal are mixed with chlorine gas, are 52.0 g of sodium chloride produced?

8. 2Na Cl2  2NaCl g
20.4 g
mol NaCl
mol Na

9. example cont’d mol bridge
They can only talk mol language from the balanced equation!
20.4 g Na
2 mol Na
2mol NaCl
= 51.9 g NaCl
1 mol NaCl
58.5 g NaCl
mol bridge
23.0 g Na
1 mol Na

10. example
Limestone, CaCO3, is heated to produce lime, calcium oxide, CaO, and carbon dioxide. How much limestone is required to produce 10.0 g of lime?

11. CaCO3  CaO + CO2 g
10.0 g
mol CaO
mol CaCO3

12. example cont’d mol bridge
They can only talk mol language from the balanced equation!
10. g CaO
1 mol CaO
1mol CaCO3
= 17.8 g CaCO3
1 mol CaCO3
100.1g CaCO3
mol bridge
56.1 g CaO

13. summary gA gB PT PT
molA
molB BE

14. 9.5 Mass Calculations: Comparing Two Reactions
we can use all this to compare; for example, which store-bought antacid is more effective by weight…
sodium bicarbonate and magnesium hydroxide are both used as antacids
if you have 1.00 g of both which will eat the most acid?

15. NaHCO3 + HCl  NaCl + H2O + CO2
1) sodium bicarb?
NaHCO3 + HCl  NaCl + H2O + CO2
1.00 g NaHCO3
1 mol NaHCO3
1 mol HCl
= 1.19 x 10-2 mol
mol bridge
84.01 g NaHCO3
1mol NaHCO3

16. 2) magnesium hydroxide? mol bridge Mg(OH)2 + 2HCl  MgCl2 + 2H2O
1.00 g Mg(OH)2
1 mol Mg(OH)2
2 mol HCl
58.33 g Mg(OH)2
1 mol Mg(OH)2
mol bridge
= 3.42 x 10-2 mol

17. Sorry, but equations Do Not describe:
1) Exact conditions
* Temperature
* Pressure
* Volume
2) What the atoms are doing (e.g. not all of them react)