Chemistry

• What does the conservation of mass state?

  No atoms are lost or made
• How is the relative atomic mass represented?

  It is the big number on the periodic table
• What is the formula for relative formula mass (Mr)?

  Sum of relative atomic masses in the formula
• What is Avogadro's constant?

  N = 6.02 x 10²³
• What is the mass of one mole of CO₂?

  44 g
• What is a limiting reactant?

  The reactant completely used up in a reaction
• What does atom economy measure?

  Amount of starting materials as useful products
• What is uncertainty in measurements?

  The interval within which the true value lies
• What is the formula to calculate moles?

  Moles = mass/Mr
• How do you calculate concentration in g/dm³?

  Concentration = concentration (mol/dm³) x Mr
• What is the formula for % yield?

  % yield = actual mass x 100 / expected mass
• What is the formula for % atom economy?

  % atom economy = Mr of desired product x 100 / sum of Mr of all reactants
• How do you calculate gas volume in dm³?

  Gas volume = moles x 24
• What are the steps to calculate unknown mass or concentration?

  1. Work out moles of known substance using n = m/Mr or n = c x v
  2. Use the equation ratio to find moles of unknown
  3. Calculate mass or concentration of unknown using m = n x Mr or c = n/v
• Why might mass appear to increase during a reaction?

  If one of the reactants is a gas added
• Why might mass appear to decrease during a reaction?

  If one of the products is a gas released
• What is the reaction equation for magnesium and oxygen?

  magnesium + oxygen → magnesium oxide
• What is the reaction equation for copper carbonate decomposition?

  copper carbonate → copper oxide + carbon dioxide