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# Stoichiometry

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### Stoichiometry

1. 1. Stoichiometry I didn’t know there would be math in Chemistry class!
2. 2. What is Stoichiometry <ul><li>Def: the study of quantitative relationships between amount of reactants used and products formed by a chemical reaction </li></ul><ul><li>Based on the Law of Conservation of Mass </li></ul><ul><ul><li>Remember… What goes in to a reaction must come out! </li></ul></ul>
3. 3. 2Na + Cl 2  2NaCl <ul><li>Use what you know about the LCM to answer the following </li></ul><ul><ul><li>How much sodium is needed to produce a certain amount of table salt? </li></ul></ul><ul><ul><li>How much chlorine is needed to produce a certain amount of table salt? </li></ul></ul><ul><ul><li>Given a certain amount of sodium or chlorine, how much table sale can be produced? </li></ul></ul>
4. 4. 4NH 3 + 5 O 2  4NO + 6H 2 O <ul><li>Coefficients represent both the numbers of particle and the numbers of moles interacting in the chemical reaction. </li></ul><ul><li>4 molecules NH 3 + 5 molecules O 2  4 molecules NO + 6 molecules H 2 O </li></ul><ul><li>OR </li></ul><ul><li>4 moles NH 3 + 5 molesO 2  4 moles NO + 6 moles H 2 O </li></ul>
5. 5. 4NH 3 + 5 O 2  4NO + 6H 2 O <ul><li>Use this to find the mass of each reactant and product. </li></ul><ul><ul><li>4 mol NH 3 (17.03g / 1 mol NH 3 ) = 68.12 g NH 3 </li></ul></ul><ul><ul><li>Molar Mass </li></ul></ul><ul><li>Do this for the remaining reactants and products </li></ul><ul><ul><li>Add the masses for the reactants and compare that to the masses of the products </li></ul></ul>
6. 6. Practice Problems Remember to balance first! <ul><li>H 2 O 2  O 2 + H 2 O </li></ul><ul><li>H 2 CO 3  H 2 O + CO 2 </li></ul><ul><li>HCl + O 2  H 2 O + Cl 2 </li></ul>
7. 7. Stoichiometric Calculations <ul><li>Mole-to-mole </li></ul><ul><li>Mole-to-mass </li></ul><ul><li>Mass-to-mass </li></ul>
8. 8. Mole-to-mole <ul><li>How can you detemine the number of moles of table salt (NaCl) producted from 0.02 moles of chlorine (Cl 2 )? </li></ul><ul><li>First, write a balanced equation. </li></ul><ul><ul><li>2Na + Cl 2  2NaCl </li></ul></ul><ul><li>Then, use the mole ratio to convert the known number of moles of chlorine to the number of moles of table salt. </li></ul><ul><ul><li>0.02 mol Cl 2 (2 mol NaCl / 1 mol Cl 2 ) = 0.04 mol NaCl </li></ul></ul>
9. 9. Try this… <ul><li>A piece of Magnesium burns in the presents of oxygen, forming magnesium oxide (MgO). How many moles of oxygen are needed to produces 12 moles of magnesium oxide. </li></ul>
10. 10. Mole to Mass <ul><li>Allows you to calculate the mass of a product or reactant in a chemical rxn. </li></ul><ul><ul><li>You need number of moles of a reactant or product. </li></ul></ul>
11. 11. 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 <ul><li>How many grams of glucose are produced when 24 moles of carbon dioxide reacts in excess water? </li></ul><ul><li>24mol CO 2 (1 mol glu / 6 mol CO 2 ) = 4 mol glu </li></ul><ul><li>4 mol glu (180.1g glu / 1 mol glu) = 721g glu </li></ul>
12. 12. Try it <ul><li>Calculate the mass of NaCl produced when 5.50 moles of Na reacts in excess Cl 2 . </li></ul><ul><li>How many grams of Cl 2 must be reacted with excess NaI to produce 6moles of NaCl. </li></ul>
13. 13. Mass to mass <ul><li>This is used to carry out a chemical reaction in a laboratory </li></ul><ul><ul><li>It would tell you how much of each reactant to use in order to produce a certain mass of product. </li></ul></ul>
14. 14. 2NaOH + H 2 SO 4  Na 2 SO 4 + 2H 2 0 <ul><li>How many grams of NaOH are needed to completely react with 50g of Sulfuric Acid to form sodium sulfate and water? </li></ul><ul><li>Convert grams of sulfuric acid to moles of NaOH </li></ul><ul><ul><li>50g SA (1mol SA / 98.09g SA)= .510 mol SA </li></ul></ul><ul><ul><li>.510mol SA (2mol NaOH / 1mol SA) = 1.02mol NaOH </li></ul></ul><ul><ul><ul><li>Molar ratio </li></ul></ul></ul><ul><li>Find the mass of NaOH needed </li></ul><ul><ul><li>1.02 mol NaOH (40g NaOH/1mol NaOH)= 40.8gNaOH </li></ul></ul>
15. 15. Try this <ul><li>If 40 g of magnesium reacts with excess HCl, how many grams of MgCl 2 are produced? </li></ul><ul><li>Determine the mass of copper needed to react completely with a solution containing 12g of AgNO 3 </li></ul>
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