Unit D Flashcards

• Gravimetric Stoichiometry


  1. Step 3: Calculate the moles of the unknown substance using a mole ratio (unknown/known)

  2. Step 4: Convert the unknown moles to mass (using equation n=m/M)
• Gravimetric Stoichiometry


  Dealing with masses, no gases present
• Example 1


  • Zinc metal reacts with solid sulfur to produce solid zinc sulfide. Predict the mass of sulfur required to react with 25 g of zinc.
• TRICK FOR MOL RATIO

  k x uk/k
• Example 2


  • Determine the mass of oxygen required to completely burn 10.0 g of octane (C8H18(l)).
• Example 3


  • What mass of water vapour is produced when 0.702 mol of hydrogen [H2(g)] burn completely in an excess of oxygen?
• Example 4


  • How many grams of copper metal will react with 0.010 moles of silver nitrate solution?
• Example 5


  • How many grams of sodium ion will be produced from the decomposition of 0.85 moles of sodium hydrogen phosphate [Na2HPO4(aq)]?
• Percent yield = actual yield/predicted yield x 100%
• Percent error = (actual - predicted)/predicted x 100%
• Predicted yield


  Mass of a product predicted from gravimetric stoichiometry of a reaction (need balanced equation and mole ratio)
• Actual yield


  Mass of product actually produced during the experiment
• Example 6


  • Percent yield = 90%, Percent error = 10%
• Example 7


  • Predicted mass = 2.93 g, Percent yield = 95.9%
• Reasons for difference between predicted and actual yield: measurement error, impure reactants, loss of product during washing
• Gas Stoichiometry


  1. Step 1: Write balanced chemical reaction

  2. Step 2: Convert given information to moles

  3. Step 3: Calculate moles of unknown using mole ratio

  4. Step 4: Convert unknown moles to final desired value
• Gas Stoichiometry


  Uses gas volume, pressure, temperature, molar volume, and ideal gas law
• Example 1


  • What mass of solid sulfur is required to produce 112 L of sulfur dioxide at STP?
• Example 2


  • Calculate the volume of hydrogen gas at SATP produced by adding 10.0 g of iron (III) solid to an excess of sulfuric acid solution.
• Example 3


  • What mass of ammonium sulfate can be produced from 75.0 kL of ammonia at 10.0°C and 110 kPa?
• Example 4


  • What volume of oxygen is required to completely combust 100 L of propane [C3H8(g)] at the same conditions?
• Example 5


  • What mass of sodium is required to produce 3.00L of hydrogen gas at 700mmHg and 25oC?
• Solution Stoichiometry


  1. Step 1: Write balanced chemical reaction

  2. Step 2: Convert given measurement to moles

  3. Step 3: Calculate moles of unknown using mole ratio

  4. Step 4: Convert unknown moles to final desired value
• Solution Stoichiometry


  Application of stoichiometric calculation principles to substances in solution
• Example 1


  • What volume of 0.125 mol/L sodium hydroxide is required to react completely with 15.0 mL of 0.100 mol/L aluminum sulfate?
• Example 2


  • In a chemical analysis, a 10.0 mL sample of phosphoric acid solution, H3PO4, was reacted with 18.2 mL of 0.259 mol/L potassium hydroxide. Calculate the amount concentration of the phosphoric acid.
• Example 3


  • A white precipitate was formed in the reaction of silver nitrate and sodium sulfate. What is the amount concentration of 100 mL of silver nitrate if 5.47 g of precipitate was recovered.
• Example 4


  • What is the concentration of the cation produced when 25.0 grams of ammonium carbonate is dissolved in 100 mL of water?
• Example 5


  • Calculate the volume of 5.00 mol/L hydrogen bromide solution needed to completely neutralize 600.0 mL of 1.25 mol/L sodium hydroxide solution.
• Example 6


  • Calculate the volume of 4.00 mol/L hydrogen bromide solution needed to completely neutralize 400.0 mL of 1.35 mol/L sodium hydroxide solution.