Announcements. discussion tomorrow. tomorrow. 10/15 (Type I) and Wednesday, 10/17 (Type II) by 7:00pm. 1. Bring handout from Tuesday to

Transcription

1 Announcements 1. Bring handout from Tuesday to discussion tomorrow. 2. Lab write-up and text W due tomorrow. 3. Electronic omework due Monday, 10/15 (Type I) and Wednesday, 10/17 (Type II) by 7:00pm

2 Stoichiometry Calculate amounts of reactants or products based on a given amount of reactant or product Example: chocolate chip cookie recipe Recipe gives us ratios of ingredients needed to make a batch of cookies

3 Stoichiometry We need to compare the ratios of what we are given to what we need 2¼ cups flour 1 teaspoon baking soda 1 teaspoon salt 1 cup butter Recipe makes 5 dozen (60) cookies 1½ cups sugar 1 teaspoon vanilla extract 2 eggs 2 cups chocolate chips ow much flour would we need if we wanted to make 120 cookies? 4½ cups flour ow many cookies could we make if we only had one cup of chocolate chips?

4 Clicker #1 ow many cookies can we make if we only have one cup of chocolate chips? A) 30 B) 40 C) 60 D) 120

5 Limiting Reactants Being able to determine amount of product you can make is very important in chemistry When you are given amounts of reactants, we must consider which one limits how much product we can make (like the chocolate chips) This is referred to as the limiting reactant

6 Stoichiometry Equations are like recipes Balanced equation gives us the ratios of reactants and products Coefficients give us the amount we need (can be in number of moles or number of particles)

7 bonds broken bonds formed

8 2 2 (g) + 2 (g) 2 2 (l)

9 Limiting Reactants 2 2 (g) + 2 (g) 2 2 (l) If you have 8 moles 2 and all the 2 you need, how many moles of 2 can you make? Need to compare ratio of reactant to product (look at coefficients)

10 Clicker #2 If you have 8 moles of hydrogen and all the oxygen you need, how many moles of water can you make? A) 1 mol B) 2 mol C) 4 mol D) 8 mol E) 16 mol

11 Limiting Reactants 2 2 (g) + 2 (g) 2 2 (l) If you have 8 moles 2 and all the 2 you need, how many moles of 2 can you make? 8 mol 2 * (2 mol 2 /2 mol 2 ) = 8 mol 2

12 Limiting Reactants 2 2 (g) + 2 (g) 2 2 (l) If you have 6 moles 2 and all the 2 you need, how many moles of 2 can you make? Need to compare ratio of reactant to product (look at coefficients)

13 Clicker #3 If you have 6 moles of oxygen and all the hydrogen you need, how many moles of water can you make? A) 1 mol B) 2 mol C) 3 mol D) 6 mol E) 12 mol

14 Limiting Reactants 2 2 (g) + 2 (g) 2 2 (l) If you have 6 moles 2 and all the 2 you need, how many moles of 2 can you make? 6 mol 2 * (2 mol 2 /1 mol 2 ) = 8 mol 2

15 Limiting Reactants 2 2 (g) + 2 (g) 2 2 (l) If you have 8 moles of 2 and 6 moles of 2, how many moles of 2 can you make? Need to compare ratios of reactants to each other

16 Clicker #4 If you have 8 moles of hydrogen and 6 moles of oxygen, how many moles of water can you make? A) 6 mol B) 8 mol C) 12 mol D) 14 mol E) 16 mol

17 8 mol 2 * (1 mol 2 /2 mol 2 ) = 4 mol 2 4 moles of 2 needed to react with 8 moles of 2, and we have 6 moles of 2 available That makes 2 the limiting reactant! 8 mol 2 * (2 mol 2 /2 mol 2 ) = 8 moles 2

18 2 2 (g) + 2 (g) 2 2 (l)

19 2 2 (g) + 2 (g) 2 2 (l) So how much 2 would we need to react with 6 moles of 2? 6 moles 2 * (2 mol 2 /1 mol 2 ) = 12 moles 2

20 Clicker #5 If you have 8 moles of nitrogen and 18 moles of hydrogen, how many moles of ammonia can you make? N N 3 A) 8 mol B) 12 mol C) 16 mol D) 18 mol E) 24 mol

21 Limiting Reactants N N 3 8 mol N 2 * (3 mol 2 /1 mol N 2 ) = 24 moles 2 Since we only have 18 moles 2 available, 2 is the limiting reactant 18 mol 2 * (2 mol N 3 /3 mol 2 ) = 12 moles N 3

22 Limiting Reactants nce a reactant is consumed (used up), no more reaction can occur DEM: range juice to Strawberry float

23 Limiting Reactants What is happening here? Methyl orange indicator is yellow-orange color in basic solution; turns red in acidic solution First contained sodium bicarbonate (basic) so solution was orange

24 Limiting Reactants Added Cl solution (acidic) NaC 3 (aq) + Cl(aq) NaCl(aq) + 2 (l) + C 2 (g) After enough Cl is added, all NaC 3 is consumed (p is neutral) If we keep adding Cl, no more reaction occurs so the solution becomes acidic and the color changes to red

25 Starting with Mass If you have 48.0 g of oxygen and all the hydrogen you need, what mass of water is produced?

26 Example #1 N N g N 2 reacts with g 2 What mass of N 3 is produced?

27 Example #2 N N g N 2 reacts with 10.0 g 2 What mass of N 3 is produced? ow much (in grams) of which reactant is leftover?