Why are the crucible and life heated at the beginning of the experiment before being weighed?
This ensures that the crucible is clean and dry. The heating process removes impurities, such as sweat and unwanted chemicals by vaporisation so that the true mass of the crucible can be weighed. The impurities will add extra mass (source of error) 4. Identify four possible sources of error in this experiment (apart from faulty equipment or incorrect reading of the balance) and analyse how they would affect your calculated ratio. Touching the crucible with hands. This may have resulted in the transfer of moisture from the hands i.e. sweat to the crucible. The extra sweat and moisture may have added unnecessary mass to the crucible, which affected the percentage composition and hence, the empirical formulae results. This would increase the value (in miniscule amounts) The magnesium coil may not have fully reacted. This meant that not all of the magnesium was combined with the oxygen. This would have affected the mass of the Magnesium Oxide, which would in turn effect the percentage comp
