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Procedure Checklist

Procedure Checklist. Safety Equipment? How much water (ml) do you measure out? How much reactant will you use? When do you weigh dry ingredients? How do you find the mass of the water? How do you insure that no gas escapes during the experiment? How do you find the mass of the reactants?

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Procedure Checklist

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  1. Procedure Checklist • Safety Equipment? • How much water (ml) do you measure out? • How much reactant will you use? • When do you weigh dry ingredients? • How do you find the mass of the water? • How do you insure that no gas escapes during the experiment? • How do you find the mass of the reactants? • How do you find the mass of the products?

  2. Basic Skills needed ex: Ca3(PO4)2 • Finding the gram formula mass • separate the elements • look up the atomic mass in the periodic table • figure out how many of each atom are in the formula • subtotal the masses of the elements • Find the total mass of the compound. x 3 x 2 x 8 = 120 = 62 = 128 Ca P O 3 2 8 40 31 16 = 310g mole

  3. Your Turn: Find the gfw for the following compounds: • Mg (OH)2 • KOH • MgCl2 • CaF2 • Na2O • Cu3(PO4)2 • KCl 58g/mole Mg(OH)26 56g/mole KOH 94 g/mole MgCl2 78 g/mole CaF2 62 g/mole Na2O 381 g/mole Cu3(PO4)2 74 g/mole KCl

  4. Stoichiometry (Chapter 9 Black Book) • READ and UNDERLINE important parts of the problem. • Write Balanced Formulas • + = - ex: Ca2+ and P3- make Ca3P2 each having 6 charges • 6+ balances out 6- • Write Balanced Equations • use coeficients to make atoms in reactants = same atoms in products • Find moles of “known” • Find moles of “unknown” • Make sure the questions are answered.

  5. What mass of NH4Cl can be produced from 7.87 grams of NH3. NH3 + HCl → NH4Cl __________________________________ _______________________________ First, identify knowns and unknowns • Known: 7.87 g NH3 • Unknown: ? g NH4Cl Next, to convert the mass of NH3 to moles you must find the gram formula weight (gfw) of ammonia, NH3 =14 N = 14 H = 1 3 x 3 =3 ------ 17 g/mole NH3

  6. What mass of NH4Cl can be produced from 7.87 grams of NH3. NH3 + HCl → NH4Cl __________________________________ _______________________________ • Known: 7.87 g NH3= ? mole • Unknown: ? g NH4Cl Now that you know that NH3 has a gfw (gram formula weight of 17 g/mole, you convert grams ammonia to moles of ammonia. 7.87 g NH3 = 0.463 moles NH3 ------ 17 g/mole NH3

  7. What mass of NH4Cl can be produced from 7.87 grams of NH3. NH3 + HCl → NH4Cl __________________________________ _______________________________ • Known: 7.87 g NH3 = 0.463 mole • Unknown: ? g NH4Cl = .463 mole Now that you know that we have 0.463 mole of NH3, we use the balanced chemical equation to determine that for every 1 mole of NH3 we make 1 mole of NH4Cl. 1 mole NH4Cl = 0.463 moles NH4Cl 0.463 moles NH3 ----------------------- 1 mole NH3

  8. What mass of NH4Cl can be produced from 7.87 grams of NH3. NH3 + HCl → NH4Cl __________________________________ _______________________________ • Known: 7.87 g NH3 = 0.463 mole • Unknown: ? g NH4Cl = 0.463 mole Now that you know that we have 0.463 mole of NH4Cl, we find the gfw (gram formula weight) of NH4Cl. =14 N = 14 H = 1 Cl = 35 x 4 = 4 4 =35 53 g/mole NH4Cl

  9. What mass of NH4Cl can be produced from 7.87 grams of NH3. NH3 + HCl → NH4Cl __________________________________ _______________________________ • Known: 7.87 g NH3 = 0.463 mole • Unknown: ? g NH4Cl = 0.463 mole Now that you know that we have 0.463 mole of NH4Cl, and the gfw (gram formula weight) of NH4Cl is 53g/mole, we can calculate the number of grams ammonium chloride. (0.463 mole NH4Cl) 53 g/mole NH4Cl = 24.5 g NH4Cl

  10. Try another: • What mass of Mg(OH)2 will react with 1.20 grams of HCl. • Mg(OH)2 + 2 HCl -> MgCl2 + 2 H2O 2 1 1.20 g 0.97 grams  (36 g/mole HCl) x 58g/mole Mg = 24 2O = 32 2H = 2 = 58g/mole 0.033 moles HCl 0.017

  11. Try another: • What mass of Ca(OH)2 will react with 2.40 grams of HCl. • Ca(OH)2 + 2 HCl -> CaCl2 + 2 H2O 2 1 2.40 g 2.5 grams  (36 g/mole HCl) x 74 g/mole Ca = 40 2O = 32 2H = 2 = 74g/mole 0.067 moles HCl 0.033

  12. Try another: • What mass of CaCl2 will form when 2.40 grams of HCl react. • Ca(OH)2 + 2 HCl -> CaCl2 + 2 H2O 2 1 3.7 g CaCl2 2.40 g ? x 110 g/mole CaCl2  (36 g/mole HCl) 0.067 moles HCl Ca = 40 2Cl = 70 = 110g/mole 0.033 moles CaCl2

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