Review Self-Quiz for Stoichiometry 1.Write the formula for a compound made from sodium and chlorine. 2.Write a chemical reaction for the following: Na reacts with chlorine, Cl 2, to form sodium chloride. 3.Find the gram formula weight of Cl 2. 4.Find the gram formula weight of NaCl Na + and Cl - → N a C l 2 Na + Cl 2 → 2 NaCl 2 Cl = 35 x 2 = 70 g/mole Na = 23 Cl = g/mole

Basic Skills Looking up the mass of elements in the periodic table: 1.Li 2.Na 3.Ca 4.Cu 5.Fe 6.N 7.O 8.Cl 9.S 10.Br amu or g/mole amu or g/mole amu or g/mole amu or g/mole amu or g/mole amu or g/mole amu or g/mole amu or g/mole amu or g/mole amu or g/mole

Basic Skills needed 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. ex: Al 2 (SO 4 ) 3 Al S O x 2 x 3 x 12 = 54 = 96 = 192 = 342g mole

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.

Your Turn: Find the gfw for the following compounds: 1.Ca (OH) 2 2.NaOH 3.CaCl 2 4.MgF 2 5.K 2 O 6.Zn 3 (PO 4 ) 2 7.NaCl answers: Ca(OH) 2 = 74 g/mole NaOH = 40 g/mole CaCl 2 = 110 g/mole MgF 2 = 62 g/mole K 2 O = 94 g/mole Zn 3 (PO 4 ) 2 = 385 g/mole NaCl = 58 g/mole

What mass of NH 4 Cl can be produced from 7.87 grams of NH 3. NH 3 + HCl → NH 4 Cl Known: 7.87 g NH 3 Unknown: ? g NH 4 Cl _______________________________ __________________________________ Next, to convert the mass of NH 3 to moles you must find the gram formula weight (gfw) of ammonia, NH 3 N = 14 H = 1 3x 3=3 = g/mole NH 3 First, identify knowns and unknowns

What mass of NH 4 Cl can be produced from 7.87 grams of NH 3. NH 3 + HCl → NH 4 Cl Known: 7.87 g NH 3 = ? mole Unknown: ? g NH 4 Cl _______________________________ __________________________________ Now that you know that NH 3 has a gfw (gram formula weight of 17 g/mole, you convert grams ammonia to moles of ammonia g/mole NH g NH 3 = moles NH 3

What mass of NH 4 Cl can be produced from 7.87 grams of NH 3. NH 3 + HCl → NH 4 Cl Known: 7.87 g NH 3 = mole Unknown: ? g NH 4 Cl =.463 mole _______________________________ __________________________________ Now that you know that we have mole of NH 3, we use the balanced chemical equation to determine that for every 1 mole of NH 3 we make 1 mole of NH 4 Cl = moles NH 4 Cl 1 mole NH 4 Cl 1 mole NH moles NH 3

What mass of NH 4 Cl can be produced from 7.87 grams of NH 3. NH 3 + HCl → NH 4 Cl Known: 7.87 g NH 3 = mole Unknown: ? g NH 4 Cl = mole _______________________________ __________________________________ Now that you know that we have mole of NH 4 Cl, we find the gfw (gram formula weight) of NH 4 Cl. N = 14 H = 1 Cl = 35 4 x 4= 4 =35 =14 53 g/mole NH 4 Cl

What mass of NH 4 Cl can be produced from 7.87 grams of NH 3. NH 3 + HCl → NH 4 Cl Known: 7.87 g NH 3 = mole Unknown: ? g NH 4 Cl = mole _______________________________ __________________________________ Now that you know that we have mole of NH 4 Cl, and the gfw (gram formula weight) of NH 4 Cl is 53g/mole, we can calculate the number of grams ammonium chloride. 53 g/mole NH 4 Cl (0.463 mole NH 4 Cl) = 24.5 g NH 4 Cl

Try another: What mass of Mg(OH) 2 will react with 1.20 grams of HCl. Mg(OH) HCl -> MgCl H 2 O 1.20 g  (36 g/mole HCl) moles HCl Mg = 24 2O = 32 2H = 2 = 58g/mole x 58g/mole 0.97 grams

Try another: What mass of Ca(OH) 2 will react with 2.40 grams of HCl. Ca(OH) HCl -> CaCl H 2 O 2.40 g  (36 g/mole HCl) moles HCl Ca = 40 2O = 32 2H = 2 = 74g/mole x 74 g/mole 2.5 grams

Try another: What mass of CaCl 2 will form when 2.40 grams of HCl react. Ca(OH) HCl -> CaCl H 2 O 2.40 g  (36 g/mole HCl) moles HCl 21 Ca = 40 2Cl = 70 = 110g/mole moles CaCl 2 x 110 g/mole CaCl g CaCl 2 ?