4/27/16 Today I will define stoichiometry and calculate mole-mole stoichiometry problems Warm Up Write a balanced equation for the reaction of magnesium.

4/27/16 Today I will define stoichiometry and calculate mole-mole stoichiometry problems Warm Up Write a balanced equation for the reaction of magnesium hydroxide and lithium.

The Mathematics of Chemical Equations
Chapter 11

Stoichiometry The study of quantitative, or measurable, relationships that exist in chemical formulas and chemical reactions. N2H H2O2  N2 + 4 H2O If I know how much N2H4 I start with, can I figure out how much water I will produce??

Stoichiometry Let’s take another look at balanced equations!
N2H H2O2  N2 + 4 H2O This equation can be interpreted as: 1 mole N2H4 reacts with 2 moles H2O2 to produce mole N2 and 4 moles H2O! So.. If I start with 1 mole N2H4, I’ll get 4 moles water!

Mole-Mole Relationships
Use a balanced chemical equation to determine the mole – mole relationship between any two substances. N2H H2O2  N2 + 4 H2O According to this equation: 1 mol N2H4 = 2 mol H2O2 1 mol N2H4 = 1 mol N2 1 mol N2H4 = 4 mol H2O 2 mol H2O2 = 1 mole N2 1 mole N2 = 4 mole H2O These are called mole to mole ratios!

x mol N2H H2O2  N2 + 4 H2O For example… 1 mol N2H4 = 2 mol H2O2 We can use this equality to factor label! How many mole of H2O2 will react with mol N2H4? 2.3 mol N2H4 2 mol H2O2 = 4.6 mol H2O2 X 1 mol N2H4

How many moles of HCl are needed to react with 0.56 moles of Zn? You must FIRST write a BALANCED EQUATION!! HCl + Zn  What is the mole-mole ratio between HCl and Zn? 2 mole HCl = 1 mole Zn 0.56 mole Zn x mol 0.56 mol 2 ZnCl2 + H2 2 mol HCl X = 1.12 mol HCl 1 mol Zn

How many moles of Na are needed to produce 55.5 moles of NaCl in the synthesis of salt? Na + Cl2  What is the mole-mole ratio between Na and NaCl? 2 mole Na = 2 mole NaCl 55.5 mole NaCl x mol 55.5 mol 2 2 NaCl 2 mol Na X = 55.5 mol Na 2 mol NaCl

How many moles of Al(OH)3 are produced when 2.53 moles of H2O react with Al2O3 in a synthesis reaction? Al2O H2O  What is the mole-mole ratio between H2O & Al(OH)3? 3 mole H2O = 2 mole Al(OH)3 2.53 mole H2O x mol 2.53 mol 3 2 Al(OH)3 2 mol Al(OH)3 X = 1.69 mol Al(OH)3 3 mol H2O

Homework Mole Ratio Practice

4/28/16 Today I will solve stoichiometric problems involving quantities other than moles Warm Up From Monday’s warm up: Write a balanced equation for the reaction of magnesium hydroxide and lithium. If 13.5 moles of magnesium were produced, how many moles of lithium must have been reacted?

Stoichiometry Problems
Using the relationships we developed in chapter 10 along with our mole to mole ratios to determine unknown amounts besides moles! 1 mol = formula mass(g) 1 mol = 6.02 x 1023 particles 1 mol = 22.4L at STP

Multi-Step Problems If you have/want something other than moles, you just have to convert! Mole:mole ratio convert convert Quantity of given Moles of given Moles of unknown Quantity of unknown

Multi-Step Problems Convert to moles Mole:Mole Ratio
Convert to what you want Mole:mole ratio convert convert Quantity of given Moles of given Moles of unknown Quantity of unknown

Multi-Step Problems Al + Fe2O3  2 2 Fe + Al2O3
What mass of aluminum oxide is produced from 2.3 g of aluminum in the following (unbalanced)reaction? Al + Fe2O3  mole-mole ratio? 2 mole Al = 1 mole Al2O3 2.3 g Al 2.3 g x grams 2 2 Fe + Al2O3 Grams of Al Moles of Al convert Moles of Al2O3 Mole:mole ratio Grams of Al2O3 1 mol Al 1 mol Al2O3 102.0 g Al2O3 X X X 27.0 g Al 2 mol Al 1 mol Al2O3 = 4.3 g Al2O3

Other Quantity Problems
If 4.0 g of sodium bicarbonate decomposes as shown at STP, what volume of carbon dioxide will be produced? NaHCO3  mole-mole ratio? 2 mole NaHCO3 = 1 mole CO2 4.0 g NaHCO3 4.0 g X L 2 Na2CO3 + H2O + CO2 Grams of NaHCO3 Moles of NaHCO3 convert Moles of CO2 Mole:mole ratio Liters of CO2 1 mol NaHCO3 1 mol CO2 22.4 L CO2 X X X 84.0 g NaHCO3 2 mol NaHCO3 1 mol CO2 = 0.53 L CO2

Multi-Step Problems Sometimes you will still be given moles or asked for moles. In this case, you can skip that conversion! Quantity of given Moles of given convert Moles of unknown Mole:mole ratio Quantity of unknown

Multi-Step Problems F2 + KBr  2 2 KF + Br2
How many molecules of bromine are produced when fluorine reacts with 3.55 moles of potassium bromide? F KBr  mole-mole ratio? mole KBr = 1 mole Br2 3.55 mole KBr 3.55 mol x molecules 2 2 KF + Br2 Grams of given Moles of KBr convert Moles of Br2 Mole:mole ratio moleculesof Br2 1 mol Br2 6.02 x 1023 molecules Br2 X X = 1.06 x 1024 molecules Br2 2 mol KBr 1 mol Br2

Multi-Step Problems In review: 1. Convert to Moles (if needed)
2. Mole:Mole Ratio 3. Convert to what you need (if needed)

Homework Stoichiometry Practice

4/29/16 Today I will practice stoichiometry problems Warm Up
If g of O2 react in the equation below, how many liters of water will be produced? 2 C6H O2  6 H2O + 12 CO2

Homework Stoichiometry Mixed Problems

5/2/16 Today I will determine the limiting reactant in a chemical reaction. Warm Up: 2Na + 2H2O  2NaOH + H2 What mass of Na is required to produce 5.68 L H2 gas at STP?

Limiting Reactant Pink Paint 1 can red : 2 cans white
How many pinks could I make with 4 cans of red and 6 cans of white? We are limited by the number of white cans.

Limiting Reactant H2 + Br2  2HBr 1mole H2 : 1 mole Br2
When exact ratios are present, they are said to be in stoichiometric proportion. (no left overs) Rarely have stoichiometric proportions…. What if you have 0.5 mole H2 and 1.2 moles Br2? 0.5 moles H2 would use up 0.5 moles Br2 0.7 moles Br2 would be left over! We are limited by the amount of hydrogen!

Limiting Reactant Limiting Reactant – the reactant that is completely used up in a chemical reaction therefore determining the maximum amount of product that can be formed Reactants with left over amounts are called excess reactants.

Limiting Reactants Cu + 2AgNO3  Cu(NO3)2 + 2Ag
If 3.5 grams of copper(II) is added to a solution containing 6.0 g silver nitrate, how many grams of silver will be formed? Cu + 2AgNO3  Cu(NO3)2 + 2Ag The reactant that would produce the smaller amount would be used up first and the reaction would stop! 3.5 g 6.0 g x g

Limiting Reactants Cu + 2 AgNO3  CuNO3 + 2 Ag
If 3.5 grams of copper(I) is added to a solution containing 6.0 g silver(I)nitrate, how many grams of silver will be formed? Cu + 2 AgNO3  CuNO3 + 2 Ag AgNO3 is limiting! So, 3.8 g Ag are actually produced! 3.5 g 6.0 g x g

Limiting Reactants 2 Na + Cl2  2 NaCl
Determine the mass of NaCl produced when 1.2 mol of Na react with .85 mol Cl2. 2 Na + Cl2  2 NaCl Na is limiting! So, 70.2 g NaCl are actually produced! 1.2 mol 0.85 mol x g

Limiting Reactants 3ZnO + 2Al(NO3)3  Al2O3 + 3Zn(NO3)2
Considering 25.0 g of ZnO react with 0.55 moles of Al(NO3)3. How many grams of Al2O3 will be produced? 3ZnO + 2Al(NO3)3  Al2O3 + 3Zn(NO3)2 ZnO is limiting! So, 10.4 g Al2O3 are produced! 25.0 g 0.55 mol x g

Homework Limiting Reactant Practice

5/3/16 Today I will calculate percent yield Warm Up –
If I think I will get 50 grams of H2O from a reaction, but I only get 35 grams, what percent of the water did I get back?

Percent Yield Expected (Theoretical) yield – amount of a product that should be produced based on calculations Actual yield – amount of product that is actually produced in the lab

Percent Yield 2Al(OH)3  Al2O3 + 3H2O
Determine the percent yield when 1.50g Al(OH)3 decomposes to produce .25g of H2O in the lab. 2Al(OH)3  Al2O3 + 3H2O actual yield 1.5 g x g expected yield

Percent Yield C6H12O6 + 6O2  6CO2 + 6H2O
123.8 g C6H12O6 burns in an excess of oxygen. If 83.4 L carbon dioxide are actually recovered in the process, what is the percent yield? C6H12O6 + 6O2  6CO2 + 6H2O xL 123.8g

Homework Percent Yield Practice

5/4/16 Today I will practice limiting reactant and percent yield problems Warm Up – When 126.2g Na reacts with an excess of oxygen, how many grams of Na2O will be formed? Na + O2  Na2O (unbalanced)

5/5/16 Today I will practice stoichiometry problems
Warm Up – If 35 grams of potassium reacts with 22 grams of sulfur, how many grams of potassium sulfide can be produced? What is the limiting reactant? 16 K + S8  8 K2S

5/9/16 Today I will review Chapter 11
Warm Up – What is the percent yield of the following reaction if 60 grams of CaCO3 is heated to give 15 grams of CaO in the lab? CaCO3→CaO + CO2

5/11/15 Today I will review Chapter 11
Warm Up – If, in the reaction below 32 grams of C2H6 actually produces 44 grams of CO2, what is the % yield? 2C2H6 + 7O2  4CO2 + 6H2O

4/27/16 Today I will define stoichiometry and calculate mole-mole stoichiometry problems Warm Up Write a balanced equation for the reaction of magnesium.

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4/27/16 Today I will define stoichiometry and calculate mole-mole stoichiometry problems Warm Up Write a balanced equation for the reaction of magnesium.

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