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Stoichiometry

Stoichiometry. We be cooking…. Stoichiometry. Deals with the chemistry of quantifying chemical reactions through the use of: Balancing equations Moles (mol) Molarity (mol/L) Mass (grams). Cooking…. A recipe is used to make a dish…let’s say brownies ½ cup butter 2 oz of chocolate

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Stoichiometry

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  1. Stoichiometry We be cooking….

  2. Stoichiometry • Deals with the chemistry of quantifying chemical reactions through the use of: • Balancing equations • Moles (mol) • Molarity (mol/L) • Mass (grams)

  3. Cooking… A recipe is used to make a dish…let’s say brownies ½ cup butter 2 oz of chocolate 1 cp sugar 2 eggs 1 tsp vanilla 2/3 cp flour ½ tsp baking powder ¼ tsp salt 24 Brownies

  4. What if I want 36 Brownies The ingredients don’t change but the amount does proportionally… ½ cup butter 2 oz of chocolate 1 cp sugar 2 eggs 1 tsp vanilla 2/3 cp flour ½ tsp baking powder ¼ tsp salt ¾ cup butter 3 oz of chocolate 1.5 cp sugar 3 eggs 1.5 tsp vanilla 1 cp flour ¾ tsp baking powder 1/8 tsp salt x by 1.5

  5. Recipes are just like chemical equations 2Mg(s) + O2(g)  2MgO(s) 2 mol of Mg + 1 mol of O2 yields 2 moles of MgO If I want 6 moles of MgO…I need 6 mol of Mg and 3 moles of O2. Proportions… Wait…wait…proportion? That means conversion!! What…DA?

  6. Coefficients are Conversion Factors 2KClO3(s)  2KCl(s) + 3O2(g) Conversions: 2 mol KClO3 = 2 mol KCl 2 mol KClO3 = 3 mol O2 2 mol KCl = 3 mol O2 Coefficients from balanced equation Question: How many moles of oxygen gas is produced if there is 4.56 moles of KClO3 present? 3 mol O2 4.56 mol KClO3 = 6.84mol of O2 2 mol KClO3

  7. So what does this mean… • From previous knowledge: • Liters to moles (Molarity) • Mass to moles (molar mass) • Now… • Moles to moles (using coefficients) • We can not only work with one particular compound/molecule/atom…now we can work with multiple compounds/molecules/atoms • All aboard to moleland!!

  8. Let’s put this knowledge into action.. 2KClO3(s)  2KCl(s) + 3O2(g) How many grams of KCl is produced if 6.89 grams of KClO3 are decomposed? Molar mass of KClO3 Molar mass of KCl Coefficients 6.89 g KClO3 1 mol of KClO3 2 74.55 g of KCl mol KCl 122.55 g of KClO3 2 mol KClO3 1 mol of KCl = 4.19 g of KCl

  9. Review Steps for Stoiching… • Write and balancing chemical reaction • Start with given (mass, moles, or volume) • Convert to moles (if mass and volume is given) • Moleland!! • Convert to moles of another compound/atom • Convert to final unit (moles/grams/volume)

  10. Working with molarity Cu(s) + 2AgNO3(aq)  2Ag(s) + Cu(NO3)2(aq) How many grams of copper will be required to completely replace silver from 208 mL of 0.100 M solution of AgNO3? Molar mass of Cu Coefficients 208 mL 1 L 0.100 mol AgNO3 1 mol Cu 63.546 g Cu 1000 mL 1 L 2 mol AgNO3 1 mol Cu = 0.661 g of Cu

  11. Reasons for Stoichiometry • Quantify how much you need to start with • Without throwing in any amount willynilly • Quantify how much you make • Determine how baller you are • Quantify how much you have left over

  12. More Practice Lead(II) nitrate solution reacts with 27.5 mL of 3.00 M carbonic acid, H2CO3(aq), how many grams of lead(II) carbonate is produced? Pb(NO3)2(aq) + H2CO3(aq)  PbCO3(s) + 2HNO3(aq) Molar mass of PbCO3 Coefficients 27.5 mL 1 L 3.00 mol H2CO3 267.21 g PbCO3 1 mol PbCO3 1000 mL 1 L 1 mol H2CO3 1 mol PbCO3 = 22.0 g of PbCO3

  13. More Practice Solid limestone, calcium carbonate, is heated to produced solid CaO and carbon dioxide gas. How much limestone is required to produce 10.0 grams of calcium oxide? CaCO3 CaO(s) + CO2(g) Molar mass of CaO Coefficients Molar mass of CaCO3 10.0 g CaO 1 mol CaO 1 mol CaCO3 100.085 g CaCO3 56.077 g CaO 1 mol CaCO3 1 mol CaO = 17.8 g of CaCO3

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