SC9 & SC10

• what is the empirical formula?

  the simplest whole number ratio of atoms or ions of each element in a substance
• what is the molecular formular?

  it represents the actual number of atom of each element in one molecule
• what are the steps to find the empirical formula?

  • mass
  • relative atomic mass
  • divide mass by relative atomic mass
  • divide answers by the smallest number to find the simplest ratio
  • then you can write the empirical formula
• what is the law of conservation of mass?

  when a solute is dissolved in a solvent to make a solution, the mass of the solution is equal to the mass of the solvent and the mass of the solute. the overall mass of the substance does not change
• how do you work out concentration using solute and solution?

  concentration= mass of solute in g/volume of solution in dm3
• what is a closed system?

  a closed system is a system that no new substances are added or removed
• what is a non-enclosed system?

  a reaction where gas can enter or escape
• what is the Avogadro constant?


  6.023 X 1023

  this many particles are in a mole
• how can you calculate the number of moles of any substance?

  number of moles of any substance = mass of substance g / (relative) formula mass
• what is a limiting reactant?


  the reactant that is used up completely in the reaction
• what is electrolysis?


  chemical decomposition produced by passing an electric current through a liquid or solution containing ions
• what is an electrolyte?

  an ionic substance with freely moving ions that can conduct electricity
• how is electrolysis done?

  it uses energy transferred by electricity to decompose electrolytes. 2 electrodes are connected to a direct current and are placed into the electrolyte. the 2 types of ions carry opposite charges and so migrate towards the opposite charge
• what are cations?


  positive ions that are attracted to the negative cathode
• what are anions?


  negative ions that are attracted to the positive anode
• what is oxidation?


  loss of electrons
• what is reduction?


  gain of electrons
• what do half equations show?

  the change at each electrode
• where does reduction take place?

  at the cathode
• where does oxidation take place?

  at the anode