1. Warmup 12/8/14 What is a chemical reaction again? What is the trick to balancing them? Objective Tonight’s Homework To see how gasses and chemical reactions relate pp 486: 15, 16 pp 487: 17, 18

2. Notes on Gasses in Chemical Equations We want to look at physical volumes of gas in equations. Example: What volume of hydrogen gas at STP can be produced when 6.54g of zinc reacts with hydrochloric acid?

3. Notes on Gasses in Chemical Equations We want to look at physical volumes of gas in equations. Example: What volume of hydrogen gas at STP can be produced when 6.54g of zinc reacts with hydrochloric acid? Woah. Look at this beast. To solve this, we’ll need to remember just about everything we learned this semester. Balancing equations, converting grams to moles, using the Ideal Gas Law…

4. Notes on Gasses in Chemical Equations First we need our equation: __ Zn + __ HCl  __ H 2 + __ ZnCl 2

5. Notes on Gasses in Chemical Equations First we need our equation: 1 Zn + 2 HCl  1 H 2 + 1 ZnCl 2

6. Notes on Gasses in Chemical Equations First we need our equation: 1 Zn + 2 HCl  1 H 2 + 1 ZnCl 2 Ok… so if we know the number of moles of zinc beforehand, we can get the number of moles of H 2 afterwards. 6.54g Zn 1 mol Zn 1 65.4g Zn Now at STP:PV = nRT V = (nRT)/P V = (0.1 mol8.31273 K)/(101.325 kPa) V = 2.24 dm 3 = 0.1 mol

7. Notes on Gasses in Chemical Equations There are a number of problems similar to this, but they all involve the same kinds of steps: - Translating grams to moles or vice versa - Writing and balancing a chemical equation - Using the Ideal Gas Law

8. Gasses in Chemical Equations Let’s see this reaction in a demo.

9. Practice Let’s wrap the class up with some practice. Turn to page 495 and do the following problems. Mr. C. will have the answers up front. 44, 45, 46, 47, 48, 49

10. Exit Question What does “STP” mean again? same total pressure stop talking please standard temperature and pressure surface tolerance or period Something to do with motor oil None of the above