Quantitative Chemistry

• What is the law of conservation of mass?

  The law of conservation of mass states that no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants.
• Define relative atomic mass.

  RAM- average mass of atoms in an element taking into account masses and abundances of its isotopes.
• Define relative formula mass.

  RFM - sun of RAM’s off all atoms in the formula.
• When measuring results, how do you increase the precision of the results?

  Use more decimal places OR use a more sensitive balance/apparatus.
• What’s Avogadro‘s constant?

  The number of atoms, molecules or ions in a mole of a given substance. The value of the constant is 6.02 x 10^23.
• What’s the formula that links mass, moles and molecular mass?

  Mass = moles x molecular mass (Mr)
• In a chemical reaction, what is meant by limiting reactant?

  Reactant that is completely consumed and limits the amount of product formed.
• Write down the two formulae that link concentration, mole/mass and volume together.

  Concentration (g/dm^3) = mass (g)/volume (dm^3)

  OR

  Concentration (mol/dm^3) = nr of moles/ volume (dm^3)
• Why is it not always possible to obtain the theoretical amount of product in a chemical reaction?

  If it’s reversible, it may not always go to completion.

  some of the product may be lost when it’s separated from the reaction mixture.

  some of the reactants may react in ways different to the expected reaction (side reactions may occur).
• How is the percentage yield of a product in a chemical reaction?

  % yield = (actual mass of a product x 100%) / maximum theoretical mass of product.