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Stoichiometry 2: grams to grams

Stoichiometry 2: grams to grams. Chemistry 2012-2013 Ms. Boon 10.18 & 10.19. Catalyst. Objectives: I can perform gram to gram conversions. Agenda: Catalyst Stoichiometry Puzzle Notes: gram to gram Practice Problems Exit Slip. Take out your homework to get a stamp.

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Stoichiometry 2: grams to grams

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  1. Stoichiometry 2: grams to grams Chemistry 2012-2013 Ms. Boon 10.18 & 10.19

  2. Catalyst Objectives: I can perform gram to gram conversions. Agenda: Catalyst Stoichiometry Puzzle Notes: gram to gram Practice Problems Exit Slip Take out your homework to get a stamp. These questions are a mini-review… We need to use these skills today in class. What is the molar mass of water? (Hint: use the periodic table.) What is the mass (grams) of 3 moles of water? How many moles is 180 g water?

  3. Helpful materials for today Objectives: I can perform gram to gram conversions. Agenda: Catalyst Stoichiometry Puzzle Notes: gram to gram Practice Problems Exit Slip Your classwork from last Thursday (the study guide) Your classwork from Monday (mole to mole conversions) Paper for notes and practice problems

  4. 4 1 Mass (grams) of COMPOUND A Mass (grams) of COMPOUND B Divide by molar mass (g/mol) of compound A Multiply by molar mass (g/mol) of compound B Multiply by mole ratio from balanced equation 3 2 Amount (Moles) of COMPOUND A Amount (Moles) of COMPOUND B Mol Compound B Mol Compound A Divide by Avogadro’s # (6.02 x 1023) Multiply by Avogadro’s # (6.02 x 1023) # particles (atoms or molecules) of COMPOUND A # particles (atoms or molecules) of COMPOUND A

  5. What are we converting?Look for clues in the question! Na2O + H2O  2NaOH • How many moles of Na2O are needed to produce 22 moles of NaOH? A: moles of NaOHtomoles of Na2O • How many grams of Na2O are needed to produce 30 moles of NaOH? A: moles of NaOHtograms of Na2O • How many moles of Na2O are needed to produce 200g of NaOH? A: grams of NaOHtomoles of Na2O • How many grams of Na2O are needed to produce 58 g of NaOH? A: grams of NaOHtograms of Na2O

  6. Quick Check • What type of conversion is this question? • How many grams of oxygen gas (O2) can be made from the decomposition of 136g of hydrogen peroxide (H2O2)? • 2 H2O2  2 H2O + O2 • Vote for your answer choice! • Grams of O2 to grams of H2O2? • Moles of O2 to grams of H2O2? • Grams of H2O2to grams of O2? • Grams of H2O2 to moles of O2?

  7. Activity: Stoichiometry Puzzle • You and your partner will receive a 12 puzzle pieces with stoichiometry problems on them. • Your task is to sort the problems into four piles according to the type of conversion in the problem. • The four types of conversions are: • Gram to gram • Mole to mole • Gram to mole • Mole to gram • When you think you have sorted the problems correctly, raise your hand to get your answers checked.

  8. Mole to Mole Conversions are part of every stoichiometry problem. Multiply by mole ratio from balanced equation Amount (Moles) of COMPOUND A Amount (Moles) of COMPOUND B Mol Compound B Mol Compound A We worked on this part earlier this week.

  9. Mass (grams) of COMPOUND A Mass (grams) of COMPOUND B Divide by molar mass (g/mol) of compound A Multiply by molar mass (g/mol) of compound B Multiply by mole ratio from balanced equation Amount (Moles) of COMPOUND A Amount (Moles) of COMPOUND B Mol Compound B Mol Compound A • Today we are adding gram to gram conversions. • We already know how to do all the steps. Today we are putting them together.

  10. Example 1: How many grams of oxygen gas (O2) can be made from the decomposition of 136g of hydrogen peroxide (H2O2)? 2 H2O2  2 H2O + O2 64g O2 Mass (grams) of COMPOUND A 136g H2O2 Mass (grams) of COMPOUND B Divide by molar mass (g/mol) of compound A Divide by 34 g/mol Multiply by molar mass (g/mol) of compound B Multiply by 32 g/mol Multiply by mole ratio from balanced equation Amount (Moles) of COMPOUND A Amount (Moles) of COMPOUND B 2 mol O2 4 mol H2O2 Mol Compound B Mol Compound A 1 molO2 2 mol H2O2

  11. Example 2: How many grams of hydrogen peroxide (H2O2) are needed to produce 180g water (H2O)? 2 H2O2  2 H2O + O2 340g H2O2 Mass (grams) of COMPOUND A 180g H2O Mass (grams) of COMPOUND B Divide by molar mass (g/mol) of compound A Divide by 18 g/mol Multiply by molar mass (g/mol) of compound B Multiply by 34 g/mol Multiply by mole ratio from balanced equation Amount (Moles) of COMPOUND A Amount (Moles) of COMPOUND B 10 mol H2O2 10 mol H2O Mol Compound B Mol Compound A 2molH2O2 2 mol H2O

  12. Mole to Mole Conversion Multiply by mole ratio from balanced equation Amount (Moles) of COMPOUND A Amount (Moles) of COMPOUND B Mol Compound B Mol Compound A Example: How many moles aluminum are needed if 3 mol Fe2O3completely react. Fe2O3 + 2 Al→ 2 Fe + Al2O3 Converting from mol Fe2O3to molAl 3 mol Fe2O3 2 molAl____ 1 molFe2O3 6 mol Al = X

  13. Gram to Gram Conversions Mass (grams) of COMPOUND A Mass (grams) of COMPOUND B Divide by molar mass (g/mol) of compound A Multiply by molar mass (g/mol) of compound B Multiply by mole ratio from balanced equation Amount (Moles) of COMPOUND A Amount (Moles) of COMPOUND B Mol Compound B Mol Compound A Example: How many grams of BrClform when 140g Cl2 react with excess Br2? Br2 + Cl2→ 2BrCl 140g Cl2 70 g/mol 2 mol Cl2 2 molBrCl 1 mol Cl2 ÷ = 4 molBrCl X X = 115 g/mol = 460 g BrCl

  14. Gram to Mole Conversion Mass (grams) of COMPOUND A Divide by molar mass (g/mol) of compound A Multiply by mole ratio from balanced equation Amount (Moles) of COMPOUND A Amount (Moles) of COMPOUND B Mol Compound B Mol Compound A Example: How many moles of BrClform when 210g Cl2 react with excess Br2? Br2 + Cl2→ 2BrCl 210g Cl2 70 g/mol 3mol Cl2 2 molBrCl 1 mol Cl2 ÷ = 6 molBrCl X =

  15. Mole to Gram Conversion Mass (grams) of COMPOUND B Multiply by molar mass (g/mol) of compound B Multiply by mole ratio from balanced equation Amount (Moles) of COMPOUND A Amount (Moles) of COMPOUND B Mol Compound B Mol Compound A Example: How many grams of BrClform when 5 mol Cl2 react with excess Br2? Br2 + Cl2→ 2BrCl 5mol Cl2 2 molBrCl 1 mol Cl2 10 molBrCl X X = 115 g/mol = 1150 g BrCl

  16. Exit Slip (3e) 10.18 & 19 Challenge: If you have 1 mol N2 and 6 mol H2 , how many moles of NH3 are produced? Why? Tonight’s HW: Read pp. 306-307, practice problems #1-4 on p. 307; problems p. 334 #1 & 3 N2 + 3 H2 2 NH3 What is the mole ratio of H2 to NH3? How many moles of H2 are needed to produce 10 moles NH3? How many moles H2 are needed to produce 170 grams NH3? (molar mass of NH3 is 17g/mol) How many grams H2 are needed to produce 170 grams NH3? (NH3 =17g/mol; H2 = 2g/mol)

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