topic 3- quantitative chemistry

• 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 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?

  They are both gases
• How can you increase the precision of results in an experiment?

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

  6.02 x 10^23
• What is the formula linking mass, molecular mass, and moles?

  Mass = Mr x Moles
• What is a limiting reactant in a chemical reaction?

  The reactant that is completely used up
• What happens during the decomposition of hydrogen peroxide?

  It forms water and oxygen gas
• What are the two formulae linking concentration, mass, and volume?

  Concentration = Mass/Volume
• What is titration?

  A technique to find solution concentration
• How do you conduct a titration?

  • Rinse pipette with unknown solution
  • Measure known volume of solution
  • Add an indicator
  • Rinse burette with known concentration
  • Gradually add known solution
  • Record volume at endpoint
  • Ensure concordant results
  • Perform calculations for concentration
• Why is it not always possible to obtain the theoretical amount of product in a chemical reaction?

  Reactions may not go to completion
• How is the percentage yield of a product calculated?

  % Yield = (Actual mass / Theoretical mass) x 100%
• What is atom economy?

  Measure of starting materials as useful products
• How do you calculate the percentage yield from given data?

  Use actual over theoretical mass