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Limiting & Excess

Limiting & Excess. Cookie Stoichiometry. How many batches could you make with… 4 eggs 6 cups of flour 2/3 cups of butter. To make one batch, it requires: 2 eggs 2 cups of flour 2/3 cups of butter. The cups of butter was your limiting reagent

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Limiting & Excess

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  1. Limiting & Excess

  2. Cookie Stoichiometry • How many batches could you make with… • 4 eggs • 6 cups of flour • 2/3 cups of butter • To make one batch, it requires: • 2 eggs • 2 cups of flour • 2/3 cups of butter • The cups of butter was your limiting reagent • The eggs and flour were your excess reagents • But how could you show this mathematically…?

  3. 2 Together…. 3 on your Own! Whiteboard!

  4. Example 1 20.00 g of H2 react with 100.0 g of O2 according to the reaction 2 H2 + O2 2 H2O Which reactant is limiting and which reactant is in excess?

  5. Example 1 1. Calculate the number of moles of a product formed.

  6. Example 1 2. Determine the limiting and excess reactants. O2 is the limiting reactant. H2 is the excess reactant.

  7. Example 1 3. To find mass of H2 in excess, find the mass of H2 which will react based on the mass of the limiting reactant.

  8. Example 1 4. Then, subtract the mass of H2 which reacts from the starting mass of H2. Mass of H2 (in excess) = mass H2 (at start) – mass H2 (reacted) = 20.00 g – 12.5g = 7.5 g

  9. Example 2 If 56.8 g of FeCl2, 14.9 g of KNO3 and 40.0 g of HCl are mixed according to the reaction 3 FeCl2 + KNO3 + 4 HCl  3 FeCl3 + NO + 2 H2O + KCl a) What is the limiting reactant?

  10. Example 2 If 56.8 g of FeCl2, 14.9 g of KNO3 and 40.0 g of HCl are mixed according to the reaction 3 FeCl2 + KNO3 + 4 HCl  3 FeCl3 + NO + 2 H2O + KCl • What is the limiting reactant? KNO3 • How many grams of each “excess” reactant left in the reaction vessel?

  11. Example 2 If 56.8 g of FeCl2, 14.9 g of KNO3 and 40.0 g of HCl are mixed according to the reaction 3 FeCl2 + KNO3 + 4 HCl  3 FeCl3 + NO + 2 H2O + KCl • What is the limiting reactant? KNO3 • b) How many grams of each “excess” reactant are actually present in excess? FeCl2= 0.8g, HCl = 18.5g

  12. Example 3 If 3.2 g of CuSO4, 2.5 g of water and 3.0 g of SO2 are reacted together in the reaction: CuSO4 + H2O + SO2 Cu + H2SO4 • Which reactant is the limiting reactant? • What is the mass of each of the excess reactants?

  13. Example 4 70.0 mL of 0.350 M ammonia (NH3) solution is mixed with 15.0 g of solid magnesium to produce magnesium nitride and hydrogen gas. • Which reactant is in excess? • How much is this particular reactant in excess by?

  14. Example 5: For the reaction: TiO2(aq)+ B4C(g)+ C(s)TiB2(aq) + CO(g) If 1150 mL of 0.800 M TiO2, 455 g of solid carbon and 1.80 L of B4C react together. Find the masses of the reactants left over.

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