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TOPIC: Predicting amounts of reagents needed or amounts of products made Do Now:

TOPIC: Predicting amounts of reagents needed or amounts of products made Do Now:. Coefficients in Chemical Equations. Numbers in front of formulas called coefficients Microscopic: Coefficients represent numbers of individual atoms or molecules Macroscopic: Coefficients give mole ratios!

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TOPIC: Predicting amounts of reagents needed or amounts of products made Do Now:

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  1. TOPIC: Predicting amounts of reagents needed or amounts of products madeDo Now:

  2. Coefficients in Chemical Equations • Numbers in front of formulas called coefficients • Microscopic: Coefficients represent numbers of individual atoms or molecules • Macroscopic: Coefficients give mole ratios! • Moles  connected to mass

  3. Coefficients in Balanced Equations MOLE-MOLE word problems: convert from moles of one substance to moles of another substance

  4. 2 C2H6 + 7 O2 4 CO2 + 6 H2O How much CO2 will be produced if 4 moles of C2H6 are consumed? 1) Start with balanced chemical equation 2) Problem will ask how many moles/liters given will yield certain amount something else 3) Use a proportion to compare old mole/liter amounts to the new mole/liter amounts

  5. = 4 moles C2H6 X moles CO2 X = 8 moles CO2 2 C2H6 + 7 O24 CO2 + 6 H2O How much CO2 will be produced if 4 moles of C2H6 are consumed?

  6. X moles H2O 5 moles C2H6 = X = 15 moles H2O 2 C2H6 + 7 O2 4 CO2 + 6 H2O How much H2O will be produced in the combustion of 5 moles of C2H6?

  7. = 5 moles X moles X = 17.5 moles O2 2 C2H6 + 7 O2 4 CO2 + 6 H2O How much oxygen will react with 5 moles of C2H6?

  8. Gas-Phase Equations • coefficients in equations represent ratio of volumes of gases involved in rxn • volume-volume word problems: rxns where ALL reactants & products are gases • volume unit (liter/milliliter) doesn’t matter as long as constant throughout

  9. = 15 L N2(g) X L H2(g) _________ _________ X = 45 L H2(g) N2(g) + 3 H2(g)  2 NH3(g) 1 How much hydrogen gas will react with 15 liters of nitrogen gas?

  10. Mass-Volume Problems • REMINDER: 1 mole any gas occupies same volume as any other gas (At STP = 22.4 L/mol) • REMINDER: 1 mole = gram formula mass • CO2 = 12 + 16 + 16 = 44 g/mol

  11. What volume of Cl2(g) measured at STP is produced when 7.65g HCl (aq) reacts with MnO2 MnO2(s) + 4HCl(aq)  MnCl2(aq) + Cl2(g) + 2H2O(l) 1. CONVERT TO MOLES 7.65g HCl mol = .2125 mols HCl 36 g HCl 2. Set up ratio 4 = 1 = .053125 mols Cl2 .2125 X 3. Convert Moles to Liters .053125 mols Cl2 22.4 L = 1.19 L 1 mol

  12. What mass of NH3(g) is produced when 2.15L of H2(g) measured at STP reacts? 3H2(g) + N2(g)  2NH3(g) • Set up Ratio 3 = 2 = 1.43 L NH3 2.15 X 2. Convert L to Moles 1.43 L mol = .064 mol NH3 22.4 L 3. Convert Moles to grams .064 mol 17 g = 1.09 g mol

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