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S’MORES

S’MORES. 1 - big marshmallow 2 - graham crackers 3 – chocolate piece Makes 1 s’more. 1 marshmallow + 2 graham crackers + 3 choco pieces  1 s’more. How many chocolate pieces are needed to make 15 smores ? … assume we have an excess of crackers & marshmallows.

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S’MORES

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  1. S’MORES 1 - big marshmallow 2 - graham crackers 3 – chocolate piece Makes 1 s’more 1 marshmallow + 2 graham crackers + 3choco pieces  1s’more How many chocolate pieces are needed to make 15 smores? … assume we have an excess of crackers & marshmallows 3 choco pieces 1 s’more 15 s’mores = choco pieces 45

  2. S’MORES 1 - big marshmallow 2 - graham crackers 3 – chocolate piece Makes 1 s’more 1 marshmallow + 2 graham crackers + 3 choco pieces  1 s’more How many marshmallows are needed if we have 150 choco pieces? … assume we have an excess of crackers. 1 marshmallow 3 choco pieces 150 choco pieces = marshmallows 50

  3. S’MORES 1 - big marshmallow 2 - graham crackers 3 – chocolate piece Makes 1 s’more 1 marshmallow + 2 graham crackers + 3 choco pieces  1 s’more How many graham crackers are needed if we have 93 choco pieces? … assume we have an excess of marshmallows. 2 crackers 3 choco pieces 93 choco pieces = crackers 62

  4. S’MORES 1 - big marshmallow 2 - graham crackers 3 – chocolate piece Makes 1 s’more 1 marshmallow + 2 graham crackers + 3 choco pieces  1 s’more How many graham crackers are needed if we have 93 choco pieces? … assume we have an excess of marshmallows. 2 crackers 3 choco pieces 93 choco pieces = crackers 62

  5. We’re using ratiosin this recipe to predict how much product (e.g. s’mores) we’ll get and how much reactant (e.g. ingredients) we’ll need. • When we do this in chemistry, it’s called “Stoichiometry” • definition: The study of the relationships between the products & reactants in a chemical reaction.

  6. 5 steps to stoichiometry • Balance the equation. • Convert your mass or volume to moles (if necessary… using molar mass). • Set up mole/mole ratios using coefficients of the 2 compounds you’re dealing with • Use mole ratios to find the moles of what you’re looking for. • Convert those moles to mass or volume (if necessary… using molar mass).

  7. Mole/mole ratio • You try this one… • Example: How many moles of potassium chloride can be made from 11 moles of potassium chlorate? 2 2 3 KClO3(s)  KCl(s) + O2(g)

  8. Mole/mole ratio • These mole ratios can be used to calculate the moles of one chemical from the given amount of a different chemical • Example: How many moles of Oxygen are needed to react with 5.00 moles of Aluminum? 4 Al + 3 O2 2 Al2O3 3 mol O2 4 mol Al 5.00 moles Al = moles O2 3.75

  9. Mole-Mass Conversions • What if the amounts are given in grams instead of moles??? • We still go through moles and use the mole ratio, but now we also use molar mass to convert moles to grams… EX. So how many moles of Al2O3 would we get if we started with 65 grams of Aluminum (and an excess of O2?) 4 Al + 3 O2 2 Al2O3 2 mol Al2O3 4 mol Al 65 g 1 mol Al = moles Al2O3 1.2 26.98 g

  10. Mole/Mass ratio Example: 15 moles of aluminum reacts with an excess of oxygen. How many grams of aluminum oxide are formed. 4 Al + 3 O2 2 Al2O3 101.96 g Al2O3 15 mol Al 2 mol Al2O3 = g Al2O3 1 mol Al2O3 4 mol Al

  11. Mole/Mass ratioYour Turn How many moles of oxygen are needed to make 100 grams of water? 2 H2 + 1 O2 2 H2O 1 mol O2 100 g H2O 1 mol H2O = mol O2 2 mol H2O 18.02 g

  12. REVIEW: Mole/mole ratio • These mole ratios can be used to calculate the moles of one chemical from the given amount of a different chemical • Example: How many moles of Aluminum oxide are needed to react with 5.00 moles of Aluminum? 4 Al + 3 O2 2 Al2O3 2 mol Al2O3 4 mol Al 5.00 moles Al = moles Al2O3 3.75

  13. REVIEW: Mole-Mass ratio • What if the amounts are given in grams instead of moles • We still go through moles and use the mole ratio, but now we also use molar mass to get to grams… EX. So how many moles of Al2O3 would we get if we started with 65 grams of Aluminum (and an excess of O2?) 4 Al + 3 O2 2 Al2O3 2 mol Al2O3 4 mol Al 65 g 1 mol Al = moles Al2O3 1.20 26.98 g

  14. Mass/Mass stoichiometry • If you’re asked for grams of “A”… • And you’re given grams of “B”… • You have a “mass/mass” stoichiometry problem :o # grams B 1 mole B # moles A# grams A # grams B # moles B 1 mole A

  15. Mass/Mass How many grams of oxygen gas can be collected from the complete decomposition of 50.0 grams of potassium chlorate? 2 KClO3(s)  2KCl(s) + 3 O2(g) 50.0 g KClO3 1 mol KClO3 3 mol O2 32.00 g O2 122.55 g KClO3 2 mol KClO3 1 mol O2 = g O2

  16. Mass/MassYour turn! How many grams of potassium chloride are produced if 25.0 g of potassium chlorate decompose? 2 KClO3 3 O2 + 2 KCl 1 mol KClO3 74.55g KCl 25g KClO3 2 mol KCl = g KCl 122.55g KClO3 1 mol KCl 2 mol KClO3

  17. Gas Stoichiometry #1 RECALL: Equal volumes of all gases at the same temperature and pressure contain the same number of molecules. -Amedeo Avogadro 3 H2(g) + N2(g)  2 NH3(g) 3moles H2 +1mole N2 2moles NH3 3liters H2 + 1liter N2 2liters NH3

  18. Gas Stoichiometry #2 How many liters of ammonia can be produced when 12 liters of hydrogen react with an excess of nitrogen? 3 H2(g) + N2(g)  2NH3(g) 12 L H2 2 L NH3 = L NH3 8.0 3 L H2

  19. Gas Stoichiometry #3 How many liters of oxygen gas, at STP, can be collected from the complete decomposition of 50.0 grams of potassium chlorate? 2 KClO3(s)  2 KCl(s) + 3 O2(g) 50.0 g KClO3 1 mol KClO3 3 mol O2 22.4 L O2 122.55 g KClO3 2 mol KClO3 1 mol O2 = 13.7 L O2

  20. Gas Stoichiometry #4 How many liters of oxygen gas, at 37.0C and 0.930 atmospheres, can be collected from the complete decomposition of 50.0 grams of potassium chlorate? 2KClO3(s)  2KCl(s) + 3O2(g) 50.0 g KClO3 1 mol KClO3 3mol O2 0.612 = mol O2 122.55 g KClO3 2mol KClO3 = 16.7 L

  21. Water from a Camel Camels store the fat tristearin (C57H110O6) in their hump. Animals burn fat for energy, but camels can also capture the water from this reaction. 2 C57H110O6(s) + 163 O2(g)  114 CO2(g) + 110 H2O(l) What mass of water can be made from 1.0 kg of fat? 1000 g “fat” 1 mol “fat” 110 mol H2O 18 g H2O 1 kg “fat” 890 g “fat” 2 mol “fat” 1 mol H2O g H2O 1112

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