Calculating Empirical Formulas

Question 1

(Exam-style question)

Answer 1

Question 2

Describe an experiment to determine the empirical formula of a simple compound, such as magnesium oxide.

Answer 2

• Get a crucible and heat until hot to ensure it’s clean
• Leave crucible to cool, then weigh it and weigh its lid
• Add clean magnesium ribbon to it - weigh crucible, lid and magnesium ribbon
• Heat crucible containing magnesium - put lid on crucible to stop any bits of solid escaping, but leave small gap for oxygen to enter
• Heat for around 10 mins, or until magnesium ribbon has turned white
• Allow crucible to cool and reweigh crucible with lid and contents all at once
• The mass of magnesium oxide is equal to this reading minus the initial reading for mass of crucible and lid