c3: quantitative chemistry

• What does the law of conservation of mass state?

  No atoms are lost or made
• 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
• How is relative formula mass (RFM) calculated?

  Sum of RAMs of all atoms in the formula
• What is the relative formula mass of CaF2?

  78
• What is the relative formula mass of C6H12O6?

  180
• Why do carbon dioxide and water escape from the test tube in the reaction?

  They are both gases
• How do you calculate the mean mass of magnesium produced from the experiment?

  (3.3 + 3.5 + 3.2) / 3 = 3.3
• 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 does Avogadro's constant represent?

  Number of atoms, molecules, or ions in a mole
• What is the formula linking 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
• What is the amount of carbon dioxide in moles in 0.32 g?

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

  Use the balanced equation and moles of ammonia
• What is the ratio of nitrogen to ammonia in the reaction?

  1:2
• What is the mass of nitrogen needed to form 6.8 tonnes of ammonia?

  5.6 tonnes
• What is a limiting reactant in a chemical reaction?

  The reactant that is completely used up
• Why do we use an excess of one reactant in a reaction?

  To ensure all of the other reactant is used
• How do you calculate the grams of oxygen gas from 40.8 g of hydrogen peroxide?

  Use the balanced equation and moles
• What is the mass of oxygen produced from 40.8 g of hydrogen peroxide?

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

  • Concentration (g per dm³) = Mass (g) / Volume (dm³)
  • Concentration (mol per dm³) = nr of moles / Volume (dm³)
• How do you calculate the concentration of potassium hydroxide solution?

  Use neutralization reaction data
• How many moles are in 40.8 g of a substance with a molar mass of 34 g/mol?

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

  2:1
• If there are 1.2 moles of H2O2, how many moles of O2 are produced?

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

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

  • Concentration (g per dm³) = Mass (g) / Volume (dm³)
  • Concentration (mol per dm³) = nr of moles / Volume (dm³)
• How many cm³ of potassium hydroxide solution neutralized 25.0 cm³ of 2.0 moldm−3 nitric acid?

  31.0 cm³
• How do you calculate the moles of HNO3 used in the reaction?

  Concentration x volume
• What is the moles of HNO3 used if the concentration is 2 and volume is 25 cm³?

  0.05 moles
• What is the mole ratio between HNO3 and KOH in the reaction?

  1:1
• How do you calculate the concentration of KOH?

  Volume = Moles / Concentration
• What is the concentration of KOH if there are 0.05 moles and the volume is 31 cm³?

  1.61 moldm−3
• 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
  4. Rinse burette with known concentration solution
  5. Gradually add known solution until endpoint
  6. Record the volume added
  7. Perform calculations to find concentration
• Why might the theoretical amount of product not be obtained in a reaction?

  Reversible reactions and side reactions