C5: Chemical Analysis

C5: Chemical Analysis

1. Purity and Mixtures

   • Pure - something is in its natural state (substance that only contains one compound/element).
   • Mixture - A substance that contain more than one element/compound that aren't chemically bonded together E.G. crude oil.

2. Relative Formula Mass

   • E.G: What is the relative formula mass of magnesium chloride, MgCl2?
     • Mg + (2 x Cl) = 24.3 + (2 x 35.5) = 24.3 + 71 = 95.3

3. The Mole

   • Number of Moles Equation
     • Number of moles = Mass in g (of element/compound) / Mr (of element/compound)

4. Acids, Alkalis and Concentrations

   • Acids and Alkalis Neutralise Each Other
     • Acid + Alkali -> Salt + Water
   • Calculation for concentration of a solution
     • Concentration = mass of solute (in g) / volume of solvent (in dm3)

5. Titration

   • If you want to find out the concentration of some alkali, you use a pipette and pipette filler and add a set volume of the alkali to a conical flask as well as 2/3 drops of indicator. Use a funnel to kill a burette with a standard solution of an acid and record the initial volume of the acid in the burette. Using this, add the acid to the alkali a bit at a time, swirling the conical flask as you add the acid. Go slowly when you think the colour change is about to be reached. The indicator changes colour when all the alkali has been neutralised.