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Review Self-Quiz for Stoichiometry

Review Self-Quiz for Stoichiometry. Na + and Cl - → N a C l. Write the formula for a compound made from sodium and chlorine. Write a chemical reaction for the following: Na reacts with chlorine, Cl 2 , to form sodium chloride. Find the gram formula weight of Cl 2 .

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Review Self-Quiz for Stoichiometry

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  1. Review Self-Quiz forStoichiometry Na+ and Cl-→ NaCl • Write the formula for a compound made from sodium and chlorine. • Write a chemical reaction for the following: Na reacts with chlorine, Cl2, to form sodium chloride. • Find the gram formula weight of Cl2. • Find the gram formula weight of NaCl 2 Na + Cl2→ 2 NaCl 2 Cl = 35 x 2 = 70 g/mole Na = 23 Cl = 35 58 g/mole

  2. Basic Skills 6.941 amu or g/mole • Looking up the mass of elements in the periodic table: • Li • Na • Ca • Cu • Fe • N • O • Cl • S • Br 22.989 768 amu or g/mole 40.078 amu or g/mole 63.546 amu or g/mole 55.847 amu or g/mole 14.006 74 amu or g/mole 15.999 4 amu or g/mole 35.452 7 amu or g/mole 32.066 amu or g/mole 79.904 amu or g/mole

  3. Basic Skills needed ex: Al2(SO4)3 • 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 2 x 3 x 12 = 54 = 96 = 192 Al S O 2 3 12 27 32 16 = 342g mole

  4. Stoichiometry (Chapter 9 Black Book) • READ and UNDERLINE important parts of the problem. • Write Balanced Formulas • + = - • 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. Your Turn: Find the gfw for the following compounds: • Ca (OH)2 • NaOH • CaCl2 • MgF2 • K2O • Zn3(PO4)2 • NaCl answers: Ca(OH)2 = 74 g/mole NaOH = 40 g/mole CaCl2 = 110 g/mole MgF2 = 62 g/mole K2O = 94 g/mole Zn3(PO4)2= 385 g/mole NaCl = 58 g/mole

  6. 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

  7. 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

  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 = .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

  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, 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

  10. 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

  11. 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

  12. 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

  13. 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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