1. Chapter 9 + review

2. Chapter 9: Chemical quantities Information given by chemical equations –Chem. eq. tell us amt. of reactant(s) needed to get to the product(s) Non-chemistry example: 2 pieces of bread + 3 slices of meat + 1 slice of cheese  1 sandwich How many pieces of bread do I need to make 50 sandwiches?

3. Chemistry examples CO + H 2  CH 3 OH (unbalanced) What is the balanced equation? Once balanced, the coefficients can stand for molecules or moles

4. Mole to mole relationships CO + 2H 2  CH 3 OH If I want 2 moles of CH 3 OH, how many moles of CO do I need? How many moles of H 2 do I need? 2 ways we can do this: –multiply the whole equation by 2 –use a molar ratio with dimensional analysis Molar ratios are derived from the balanced equation –1 mol CO= 2 mol of H 2 = 1 mole of CH 3 OH

5. mole to mole relationship What number of moles of O 2 will be produced by the decomposition of 5.8 mol of water(Water decomposes to produce hydrogen and oxygen gases)? Step 1: Determine balanced equation Step 2 use a molar ratio to determine the answer.

6. mole to mole relationship Ammonia is used in huge quantities as a fertilizer. It is manufactured by combining nitrogen and hydrogen according to the following unbalanced equation: N 2 + H 2  NH 3 calculate the number of moles of NH 3 that can be made from 1.30 mol of H 2 reacting with excess N 2

7. Mass calculations We don’t have a mole scale, so we need to learn how to relate mass to chemical equations. Our key to solving mass calculation problems is to understand and use molar ratios. When solving problems, convert everything into moles using molar mass.

8. Mass calculations C 3 H 8 + O 2  CO 2 + H 2 O What mass of oxygen will be required to react exactly with 44.1g of C 3 H 8 ? 1.Balance the equation 2.Convert amt. of propane into moles 3.Use molar ratio to solve problem

9. Solving the problem C 3 H 8 + O 2  CO 2 + H 2 O 1.C 3 H 8 + 5O 2  3CO 2 + 4H 2 O 2.Molar mass of propane is 44.1 g/mol

10. Bellwork 1/9/2009 -Put chairs into testing formation (rows) For the reaction, fill in the table for the decomposition reaction: Get HW out to turn in KClO 3  KCl + O 2 6 mole.25 mole

11. Real world example Baking soda is often used as an antacid NaHCO 3 + HCl  H 2 O + CO 2 + NaCl Milk of Magnesia is an aqueous suspension of Mg(OH) 2 Mg(OH) 2 + 2HCl  2H 2 O + MgCl 2 Which antacid can consume the most stomach acid (1.00g baking soda or MOM)?

12. Solving the problem Convert the mass of NaHCO 3 into moles. Then determine how many moles of acid are neutralized with the NaHCO 3. Convert the mass of MOM into moles. Then determine how many moles of acid are neutralized. Which one neutralizes more acid?

13. Chap9 continued Limiting reactants

14. Limiting reactant The limiting reactant is simply the reactant that will run out first. Example: A + B  C Lets say I have 20 A and 30 B. Which one is the limiting reactant? In chemistry problems, things get complicated by the fact that different ratios of reactants are needed

15. Determine limiting reactant To do this with chemical equations, you must determine how much (moles) of product each reactant will produce. The reactant that produces the least moles of product is the limiting reactant {Divide # of moles by coefficient} Example: 2Al + 3 I 2  2AlI 3 Determine limiting reactant if you have 1.2 mol of Al and 2.40 mole of I 2.

16. Determine limiting reactant Example: 2Al + 3 I 2  2AlI 3 Which is the limiting reagent if you have 1.20 g Al and 2.40 g iodine? To solve this, you need to convert all masses into moles and then solve just like the previous problem

17. Chapter 9 Percent yield

18. Bellwork Mg(OH) 2 + HCl  H 2 O + MgCl 2 If I start with 1.8 moles of Mg(OH) 2 and 1 mole of HCl, which is my limiting reactant? How many moles of water will I be making?

19. Percent yield Theoretical yield: Amt. of product we should have gotten Actual yield: Amt of product you actually got. % yield: Actual/theoretical * 100%

20. Non-chemistry example: 2 slices of bread + 1 meat + 1 cheese  1 sandwich Let’s say that while making the sandwich, the meat and cheese fall out. So now we have ½ of a sandwich. Therefore our actual yield is ½ Our theoretical yield is 1 Our % yield is.5/1 *100% or 50%

21. Chemistry example NH 3 + HCl  NH 4 Cl Lets say I start out with 2 moles of ammonia. After doing the reaction, I find out I actually get 0.25 moles of product. What is my actual yield? What is my theoretical yield? What is my percent yield?

22. Stoichiometry problem solving Step 1: Balance the equation Step 2: If in moles, move on »If in mass, convert to moles (using molar mass) Step 3: convert from moles of what is given to moles what is desired Step 4: If mass is desired, convert from moles of what is desired into mass (using molar mass)

23. Bellwork (1/13/2009) For the balanced equation: 1 NaHCO 3 + 1HCl  1CO 2 + 1H 2 O + 1NaCl How many moles of HCl do I need to react with 2.15g of sodium bicarbonate?