Unit 7: Stoichiometry Lundquist -- 2016

Mole to mole conversions Unit 7.1 Mole to mole conversions

Review Balancing Reactants = products Keep practicing Tips: Example 1 Review Balancing Reactants = products Keep practicing Tips: Save elemental for last Keep polyatomics together If stuck double everything

Review Molar Conversions 1 mole = 6.022 x 1023 atoms All atoms have a different mass Molar mass = the mass of 1 mole Add up the mass of the elements on the periodic table Pay attention to the number of each element

Note Quiz Questions 1 2 3

Note Quiz Questions 4 5

Its like baking 2 Br + Ch  Br2Ch 2 Br = 1 Ch 2 Br = 1 Br2Ch

Mole to Mole Ratio In a balanced equation coefficients: Can be read as molecules AND moles Can be used as a conversion

Find p. 8

Its like baking 2 Br + Ch  Br2Ch If you wanted to make 173 grilled cheeses how much bread would you buy? How much cheese? 2 Br + Ch  Br2Ch

Mole to Mole Ratio 3 H2 + N2  2 NH3 Example 2 Mole to Mole Ratio 3 H2 + N2  2 NH3 How many moles of N2 are needed to react with 9 moles of H2? How many moles of NH3 will be produced? CH4 + O2  CO2 + H2O Is this reaction useable as it is written? How many mol O2 are needed to react with 0.5 mol CH4? How much H2O can be produced from 0.5 mol CH4?

Note Quiz Questions 6 7

Note Quiz Questions 8 9

Do p. 8, & 9

Particle Sketches A pictorial representation of chemical reactions which utilize shapes to differentiate between elements Pay attention to the Balanced equation!! Must match the stoichiometric relationships

Note Quiz Questions 10

Do p. 10

Mass to mass conversions Unit 7.2 Mass to mass conversions

Conservation of mass! Matter can not be created nor destroyed The reason we balance reactions If 10 grams react then 10 grams have to be produced

Example 3 𝑁 2 +3 𝐻 2 →2𝑁 𝐻 3 If 15.0 grams of ammonia (NH3) were produced from the above reaction, and 5 grams of hydrogen reacted, what was the mass of nitrogen that reacted?

Note Quiz Questions 1 Not actual stoichiometry here!!!

Its like baking 2 Br + Ch  Br2Ch If you wanted to make 173 grilled cheeses how many pounds of cheese would you have to buy? 2 Br + Ch  Br2Ch 1lb = 16 slices

Stoichiometry Find a way that works for YOU Here are the ways I know. If you learn another SHOW ME By steps Dimensional analysis Round-about ALL starts with a plan

Dimensional Analysis A way of showing units cancelling out Uses conversion factors REMEMBER mol:mol ratios are conversions MM is X g = 1 mol

Stoichiometry by Dimensional Analysis Your plan is the TOP (numerator) of your dimensional analysis Whatever UNIT came before goes below (denominator) C3H8 + 5O2  3CO2 + 4 H2O If a propane (C3H8) tank lost 48.6g of mass while running, what mass of carbon dioxide (CO2) was produced?

Practice: 2 C2H6 + 7O2  4 CO2 + 6 H2O How many grams of oxygen are required to completely burn 65.4g ethane? When 65.4g ethane is completely combusted, how many grams of carbon dioxide are produced?

Note Quiz Questions 2 3

Note Quiz Questions 4 5

Do p. 11, 12, & 13

Unit 7.3 Volume to volume

Molar Volume of a Gas ALL gases have no attractive forces VERY spread out Mainly empty space The volume of a gas is dependent on temperature and pressure

Molar Volume of a Gas 1 mole of ANY gas at standard temperature and pressure (STP) is 22.4 L Standard temperature = 0oC = 273K Standard Pressure = 1 atm

Example 5 How many moles of air are in a 2 L bottle? Rank the following based on volume 1 mol H2 0.75 mol Xe 5 g H2O vapor 5 g CO2?

Volume to volume stoichiometry H2CO3(g)  H2O(g) + CO2(g) Example 6 Volume to volume stoichiometry H2CO3(g)  H2O(g) + CO2(g) How many moles is 1.9 liters of carbonic acid (H2CO3) at STP? What is the mass of 9.3 L CO2 at 1 atm and 0oC?

Note Quiz Questions 1 2

Note Quiz Questions 3 4

Note Quiz Questions 5 6 Three balloons are filled with 1 liter of gas. One balloon is filled with argon (MM = 40g/mol), one is filled with carbon dioxide (MM = 44g/mol), and another is filled with hydrogen gas (MM = 2g/mol). Which correctly shows the relationship between the volume of each gas? Ar<H2<CO2 Ar = CO2 < H2 Ar> CO2 > H2 Ar = CO2 = H2

Volume to volume stoichiometry Simply change volume to moles, then back Since you will divide, then multiply by 22.4L/mol you could always just multiply by the mole to mole ratio.

Practice What volume of dinitrogen pentoxide can be produced from 10L of oxygen?

Note Quiz Questions 7 Given the reaction above, what volume of oxygen (O2) is needed to react with 100mL of butane (C4H10) at 1atm and 0oC? 15.4 ml 50. mL 100. mL 650mL 8 Given the reaction above, what volume of water can be captured from the complete combustion of 22.4L of butane at STP? 4.48 L 112 L 224 L 448 L

Do p. 14

Practice How many liters of nitrogen are required to react with excess oxygen to produce 100g of dinitrogen pentoxide?

Note Quiz Questions 9 What volume of oxygen is needed to react with 50 mL of nitrogen? 20.0 ml 50.0 mL 125 ml 250. mL 10 What mass of dinitrogen pentoxide can produced from 22.4L of nitrogen at 1 atm and 0oC? 22.4 g 43.2 g 108 g 216 g

Do p. 15

Quiz Next Class Balancing Mass to mass conversion Mass to volume conversion (x2) Percent yield (%𝑦𝑖𝑒𝑙𝑑= 𝑎𝑐𝑡𝑢𝑎𝑙 𝑠𝑡𝑜𝑖𝑐ℎ × 100)

Percent Yield pt 1 (YAY no note quiz! Don’t try this homework yet) Unit 7… Percent Yield pt 1 (YAY no note quiz! Don’t try this homework yet)

Yields Theoretical Yield Experimental Yield The amount of reactant/product from the stoichiometry math Expectation The amount of reactant/product from an EXPERIMENT Reality

Why Typically because of human error Products are not dry Loss from splatter/spills Residue in transfers

%𝑦𝑖𝑒𝑙𝑑= exp𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑠𝑡𝑜𝑖𝑐ℎ𝑖𝑜𝑚𝑒𝑡𝑟𝑦 ×100 Percent Yield How much you produced In a perfect world = 100% (it’s never 100% -- reality sucks) %𝑦𝑖𝑒𝑙𝑑= exp𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑠𝑡𝑜𝑖𝑐ℎ𝑖𝑜𝑚𝑒𝑡𝑟𝑦 ×100

Practice 2AgCl + Cu  CuCl2 + 2Ag A student performs the reaction above with 0.932g Cu, if 2.98g Ag is captured, what is his percent yield? Another student captured 3.4 g of Ag, what is her percent yield?

%𝑦𝑖𝑒𝑙𝑑= exp𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑠𝑡𝑜𝑖𝑐ℎ𝑖𝑜𝑚𝑒𝑡𝑟𝑦 ×100 QUIZ TIME! Remember Your mole map How you do stoich. Percent yield: %𝑦𝑖𝑒𝑙𝑑= exp𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑠𝑡𝑜𝑖𝑐ℎ𝑖𝑜𝑚𝑒𝑡𝑟𝑦 ×100

Limiting Reagents & Percent Yield Unit 7.4 Limiting Reagents & Percent Yield

Limiting Reagents Limit the amount of product that can be produced You will often have a finite supply of reagents so 1 will be used up Remaining reactants are called EXCESS ALL STOICHIOMETRY IS DONE BASED ON THE LIMITING REAGENT!

Practice: P4H10 + 6 H2O  4 H3PO4 Given 0.48mol P4H10, and 1.52 mol H2O Identify the limiting reagent Calculate the number of moles of product formed Calculate the number of moles of excess reactant remaining after the reaction has used up all the limiting reagent

Practice: 2 H2 + O2  2 H2O Given 6.4 mol H2 and 3.4 mol O2 Identify the limiting reagent Calculate the moles of product formed Calculate the number of moles of excess reactant remaining after all the limiting reagent has been used

Practice: 2 H2 + O2  2 H2O Given 6.4 mol H2 and 3.4 mol O2 Identify the limiting reagent Calculate the moles of product formed Calculate the number of moles of excess reactant remaining after all the limiting reagent has been used

Note Quiz Questions 1 Given the reaction above, if 1.45 mol of each reactant is added to a beaker, which one is the limiting reagent? Cu AgNO3 Cu(NO3)2 Ag 2 Given the reaction above, if 1.45 mol of each reactant is added to a beaker, how many moles of Ag can be captured? 0.725 mol 1.45 mol 2.90 mol No Ag can be captured

Note Quiz Questions 3 Given the reaction above what mass of rust (FeO) can be produced from 112g of iron and 64g of oxygen gas? 72.1 g 144 g 216 g 288 g

Yields Theoretical Yield Experimental Yield The amount of reactant/product from the stoichiometry math Expectation The amount of reactant/product from an EXPERIMENT Reality

Why Typically because of human error Products are not dry Loss from splatter/spills Residue in transfers Imperfect conditions

%𝑦𝑖𝑒𝑙𝑑= exp𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑠𝑡𝑜𝑖𝑐ℎ𝑖𝑜𝑚𝑒𝑡𝑟𝑦 ×100 Percent Yield How much you produced In a perfect world = 100% (it’s never 100% -- reality sucks) %𝑦𝑖𝑒𝑙𝑑= exp𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑠𝑡𝑜𝑖𝑐ℎ𝑖𝑜𝑚𝑒𝑡𝑟𝑦 ×100

Practice 2AgCl + Cu  CuCl2 + 2Ag A student performs the reaction above with 0.932g Cu, if 2.98g Ag is captured, what is his percent yield? Another student captured 3.4 g of Ag, what is her percent yield?

Note Quiz Questions 4 A student performs the above reaction with 1.01g Al and excess silver nitrate. She captures 12.5 g of Ag. What is her percent yield? 3.19% 95.9% 103 % 186% If her experiment was similar to the one you performed in class, what is a possible reason for her percent yield? The sample may still be wet She did not use enough silver nitrate The gram scales were not accurate She did not calculate her theoretical yield correctly 5

Do p. 24 & 25

THE END Test NEXT PERIOD! 20 MC you will need to 17 to get a 100 Multiple Choice homework due NEXT PERIOD! Test NEXT PERIOD! 20 MC you will need to 17 to get a 100 1 free response worth 10 points, you will need to earn 5 to get a 100