Quantative Chemistry

• What is the relative atomic mass (Ar) of an element?

  The mass of an atom of the element compared to the mass of one atom of carbon-12
• What is the relative formula mass (Mr)?

  The mass of a compound compared to the mass of one atom of carbon-12.
• How is the relative formula mass calculated?

  The Ar's of the individual elements that make up the compound are added together
• What is one mole of an substance?

  The relative molecular or formula mass of the substance in grams.
• How is the number of moles calculated?

  moles = mass (g) / Ar

  or

  moles = mass (g) / Mr
• What is the avagadro constant?

  6.02 x 10^23
• What does the avagadro constant tell you?

  The amount of particles contained within one mole of a substance
• What does a balanced symbol equation tell you about a chemical reaction?

  A balanced symbol equation shows how many moles of a substance are involved in a chemical reactions
• Why are balanced symbol equations so useful?

  Balanced symbol equations can be used to calculate the masses of reactants and products involved in a chemical reaction.
• What is the limiting factor of a reaction?

  The reactant that is used up first in a chemical reaction
• What is meant by the yield of a chemical reaction?

  Amount of product formed.
• What is the equation used to calculate the yield?

  %yield = (actual mass of product/theoretical mass of product) x100
• What factors affect the yield of a reaction?

  The reaction may be reversible

  some of the product may be lost

  some of the reactants may not have reacted
• What is the atom economy of a reaction?

  The atom economy shows the % of reactants formed into useful product
• How is atom economy calculated?

  % atom economy = (Mr of desired product/ Mr or all products) / 100
• Why is atom economy important in industrial processes?

  atom economy is important as it is important to conserve the Earth's resources and minimise pollution
• What is meant by the concentration of a solution?

  How many particles of the substance (solute) is contained within a set volume of solution
• What is meant by concentrated?

  A high mass of solute in a set volume
• What is meant by dilute?

  A low mass of solute in a set volume
• What is the equation used to calculate concentration in g/dm3?

  Concentration (g/dm3) = mass of solute (g) / volume of solution (dm3)
• What is the equation used to calculate concentration in mol/dm3?

  Concentration (mol/dm3) = number of moles / volume of solution (dm3)
• What is a titration used for?

  A titration is used to accurately measure what volume of acid and alkali react together completely.
• What is the end point of a titration?

  The end point is the point of neutralisation and is shown by a colour change of an indicator
• What are the stages of a titration calculation?

  1. balance equation;
  2. Calculate moles of substance of known concentration;
  3. find moles of unknown substance by looking at moles in equation;
  4. once the moles are known calculate the concentration of unknown substance.
• What volume does one mole of any gas occupy at room temperature and pressure?

  24dm3 or 24000cm3