PMT

• What does the law of conservation of mass state?

  No atoms are lost or made in reactions
• How does the law of conservation of mass apply to chemical reactions?

  The mass of products equals the mass of reactants
• What is the balanced equation for magnesium reacting with hydrochloric acid?

  Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g)
• What is relative atomic mass (RAM)?

  Average mass of atoms in an element
• What is relative formula mass (RFM)?

  Sum of RAMs of all atoms in a formula
• Why do carbon dioxide and water escape from the test tube in the reaction?

  They are both gases
• What is the mean mass of magnesium produced from the experiment?

  3.3 g
• How can you increase the precision of the results in the experiment?

  Measure to more decimal places
• What is Avogadro's constant?

  6.02 x 10^23
• What formula links mass, molecular mass, and moles?

  Mass = Mr x Moles
• What is the mass of 20 moles of calcium carbonate, CaCO3?

  2000 g
• How do you calculate the amount of carbon dioxide in moles from 0.32 g?

  Moles = Mass / Mr
• How many moles of carbon dioxide are in 0.32 g?

  0.007 moles
• How do you calculate the mass of nitrogen needed to form 6.8 tonnes of ammonia?

  Use moles and balanced equation
• What is the limiting reactant in a chemical reaction?

  The reactant completely used up
• How much oxygen gas is produced from 40.8 g of hydrogen peroxide?

  19.2 g
• What are the two formulas linking concentration, mass, and volume?

  Concentration = Mass/Volume; Concentration = Moles/Volume
• What is the concentration of the potassium hydroxide solution?

  Calculate using neutralization data
• What is the balanced equation for the decomposition of hydrogen peroxide?

  2 H2O2(l) → 2 H2O + O2(g)
• What is the molar mass of hydrogen peroxide (H2O2)?

  34 g/mol
• How many moles are in 40.8 g of hydrogen peroxide?

  1.2 moles
• What is the mole ratio of H2O2 to O2 in the balanced equation?

  2:1
• How many moles of O2 are produced from 1.2 moles of H2O2?

  0.6 moles
• What is the mass of oxygen produced from 0.6 moles of O2?

  19.2 g
• What are the two formulae that link concentration, mass, and volume?

  • Concentration (g per dm³) = Mass (g) / Volume (dm³)
  • Concentration (mol per dm³) = Number of moles / Volume (dm³)
• How many moles of HNO3 are used in the reaction with potassium hydroxide?

  0.05 moles
• What is the ratio of HNO3 to KOH in the neutralization reaction?

  1:1
• What is the concentration of KOH if 0.05 moles are present in 31.0 cm³?

  1.61 mol/dm³
• What is the molar volume of a gas at room temperature and pressure?

  24 dm³
• What is titration?

  A technique to find solution concentration
• What are the steps to conduct a titration?

  1. Rinse pipette with unknown solution.
  2. Measure known volume of unknown solution.
  3. Add an indicator to the solution.
  4. Rinse burette with known concentration solution.
  5. Gradually add known solution until endpoint.
  6. Record the volume added and perform calculations.
• Why might the theoretical amount of product not be obtained in a reaction?

  Reversible reactions and product loss occur
• How is the percentage yield of a product calculated?

  % Yield = (Actual mass / Theoretical mass) x 100%
• What is the % yield of NH3 if 40.5 g is produced from 20.0 mol H2?

  17.8%
• What is atom economy?

  Measure of starting materials as useful products
• Which reaction has better atom economy: CuCO3 + 2 HCl or CuO + 2 HCl?

  • Reaction II has better atom economy.
  • Total formula mass of reactants for Reaction II = 152.5.
  • Formula mass of CuCl2 = 134.5.
  • Atom economy = (134.5 / 152.5) x 100% = 88.2%.