1. Final Information Open-ended: 6/11 (review 6/10) Last day to ask questions for MC 6/14 Topics: –Bonding –Reactions Chemical Equations (balancing, types) –Percent Composition –Molar Mass, Avogadro’s Number, conversions –Empirical Formula –Stoichiometry Limiting reactants Mole-mole, grams-grams, particles-particles conversions

2. Stoichiometry

3. Flowchart Atoms or Molecules Moles Mass (grams) Divide by 6.02 X 10 23 Multiply by 6.02 X 10 23 Multiply by atomic/molar mass from periodic table Divide by atomic/molar mass from periodic table

4. molar mass Avogadro’s number Grams Moles particles molar mass Avogadro’s number Grams Moles particles Everything must go through Moles!!! Calculations

5. Chemistry Recipes Looking at a reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe) Looking at a reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe) Be sure you have a balanced reaction before you start! Be sure you have a balanced reaction before you start! Example: 2 Na + Cl 2  2 NaCl Example: 2 Na + Cl 2  2 NaCl This reaction tells us that by mixing 2 moles of sodium with 1 mole of chlorine we will get 2 moles of sodium chloride This reaction tells us that by mixing 2 moles of sodium with 1 mole of chlorine we will get 2 moles of sodium chloride What if we wanted 4 moles of NaCl? 10 moles? 50 moles? What if we wanted 4 moles of NaCl? 10 moles? 50 moles?

6. Example Questions Write the balanced reaction for hydrogen gas reacting with oxygen gas. Write the balanced reaction for hydrogen gas reacting with oxygen gas. 2 H 2 + O 2  2 H 2 O 2 H 2 + O 2  2 H 2 O How many moles of reactants are needed? How many moles of reactants are needed? What if we wanted 4 moles of water? What if we wanted 4 moles of water? What if we had 3 moles of oxygen, how much hydrogen would we need to react, and how much water would we get? What if we had 3 moles of oxygen, how much hydrogen would we need to react, and how much water would we get? What if we had 50 moles of hydrogen, how much oxygen would we need, and how much water produced? What if we had 50 moles of hydrogen, how much oxygen would we need, and how much water produced?

7. Consider : 4NH 3 + 5O 2  6H 2 O + 4NO How many moles of H 2 O are produced if 0.176 mol of O 2 are used? How many moles of NO are produced in the reaction if 17 mol of H 2 O are also produced? 6 mol H 2 O 5 mol O 2 x Stoichiometry questions (1) # mol H 2 O=0.176 mol O 2 0.2112 mol H 2 O = 4 mol NO 6 mol H 2 O x # mol NO=17 mol H 2 O 11.33 mol NO = Notice that a correctly balanced equation is essential to get the right answer

8. Consider : 4NH 3 + 5O 2  6H 2 O + 4NO How many grams of H 2 O are produced if 1.9 mol of NH 3 are combined with excess oxygen? How many grams of O 2 are required to produce 0.3 mol of H 2 O? 6 mol H 2 O 4 mol NH 3 x Stoichiometry questions (2) # g H 2 O= 1.9 mol NH 3 51.4 g H 2 O = 18.02 g H 2 O 1 mol H 2 O x 5 mol O 2 6 mol H 2 O x # g O 2 = 0.3 mol H 2 O 8 g O 2 = 32 g O 2 1 mol O 2 x

9. Mass-Mass Conversions Most often we are given a starting mass and want to find out the mass of a product we will get (called theoretical yield) or how much of another reactant we need to completely react with it (no leftover ingredients!) Most often we are given a starting mass and want to find out the mass of a product we will get (called theoretical yield) or how much of another reactant we need to completely react with it (no leftover ingredients!) Now we must go from grams to moles, mole ratio, and back to grams of compound we are interested in Now we must go from grams to moles, mole ratio, and back to grams of compound we are interested in

10. Mass-Mass Conversion Ex. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen. Ex. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen. N 2 + 3 H 2  2 NH 3 N 2 + 3 H 2  2 NH 3 2.00g N 2 1 mol N 2 2 mol NH 3 17.06g NH 3 28.02g N 2 1 mol N 2 1 mol NH 3 = 2.4 g NH 3

11. Consider : 4NH 3 + 5O 2  6H 2 O + 4NO How many grams of NO is produced if 12 g of O 2 is combined with excess ammonia? 4 mol NO 5 mol O 2 x Stoichiometry questions (3) # g NO= 12 g O 2 9.0 g NO= 30.01 g NO 1 mol NO x 1 mol O 2 32 g O 2 x

12. Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles. Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y) We can start anywhere along this path depending on the question we want to answer Q- for the reaction 2H 2 + O 2  2H 2 O what is the path we would take for the following Given 2 moles H 2 O, calculate grams H 2 O? Moles O 2 required for 36 g H 2 ? Grams of H 2 O produced from 6 grams O 2 ? Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles. Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y) We can start anywhere along this path depending on the question we want to answer Q- for the reaction 2H 2 + O 2  2H 2 O what is the path we would take for the following Given 2 moles H 2 O, calculate grams H 2 O? Moles O 2 required for 36 g H 2 ? Grams of H 2 O produced from 6 grams O 2 ? Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles. Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y) We can start anywhere along this path depending on the question we want to answer Q- for the reaction 2H 2 + O 2  2H 2 O what is the path we would take for the following Given 2 moles H 2 O, calculate grams H 2 O? Moles O 2 required for 36 g H 2 ? Grams of H 2 O produced from 6 grams O 2 ? Notice that we cannot directly convert from grams of one compound to grams of another. Instead we have to go through moles. Many stoichiometry problems follow a pattern: grams(x)  moles(x)  moles(y)  grams(y) We can start anywhere along this path depending on the question we want to answer Q- for the reaction 2H 2 + O 2  2H 2 O what is the path we would take for the following Given 2 moles H 2 O, calculate grams H 2 O? Moles O 2 required for 36 g H 2 ? Grams of H 2 O produced from 6 grams O 2 ? Converting grams to grams

13. Moving along the stoichiometry path We always use the same type of information to make the jumps between steps: grams (x)  moles (x)  moles (y)  grams (y) Molar mass of xMolar mass of y Mole ratio from balanced equation Given: 4NH 3 + 5O 2  6H 2 O + 4NO a) How many moles of H 2 O can be made using 0.5 mol NH 3 ? b) what mass of NH 3 is needed to make 1.5 mol NO? c) how many grams of NO can be made from 120 g of NH 3 ?

14. 4NH 3 + 5O 2  6H 2 O + 4NO a) b) c) Answers 6 mol H 2 O 4 mol NH 3 x # mol H 2 O=0.5 mol NH 3 0.75 mol H 2 O = 4 mol NH 3 4 mol NO x # g NH 3 = 1.5 mol NO 25.6 g NH 3 = 17.04 g NH 3 1 mol NH 3 x 4 mol NO 4 mol NH 3 x # g NO= 120 g NH 3 211 g NO= 30.01 g NO 1 mol NO x 1 mol NH 3 17.04 g NH 3 x

15. More Stoichiometry Questions Follow the rules for significant digits. Show all calculations. 1. 2 C 4 H 10 + 13 O 2 -> 8 CO 2 + 10 H 2 O a) what mass of O 2 will react with 400 g C 4 H 10 ? b) how many moles of water are formed in a)? 2. 3 HCl + Al(OH) 3 -> 3 H 2 O + AlCl 3 How many grams of aluminum hydroxide will react with 5.3 moles of HCl? 3. Ca(ClO 3 ) 2 -> CaCl 2 + 3 O 2 What mass of O 2 results from the decomposition of 1.00 kg of calcium chlorate? 4.The reaction of Ca with water can be predicted using the activity series. What mass of water is needed to completely react with 2.35 g of Ca?

16. 5.Fe 2 O 3 + 3CO -> 2Fe + 3CO 2. a) How many moles of carbon monoxide are required to react with 163.0 g of iron(III) oxide? b) How many grams of CO 2 are produced from a reaction that also produces 23.9 grams of Fe? 6. 3Cu + 8HNO 3  3Cu(NO 3 ) 2 + 4H 2 O + 2NO a) how many moles of copper(II) nitrate can be prepared from 17.0 moles of Cu? b) how many grams of copper(II) nitrate can be prepared using 3.8 moles of HNO 3 ? c) what mass of water results from the reaction of 8.50 kg of copper metal? For more lessons, visit www.chalkbored.com www.chalkbored.com