One of the most common errors in have observed for GCE O-Level Chemistry students is when they are Calculating Empirical Formulae from Composition by Mass.
Take the following question that was given to my students:
Question:
Calculate the empirical formula of a compound that has the composition: 48.8% carbon, 13.5% hydrogen and 37.7% nitrogen.
After calculations, one of my students came up confidently with the answer of C2H5N.
– which is the Incorrect Answer.
After asking her to present her working to the class, i we realised that she made a mistake when trying to round off final numbers.
Let’s take a look at my suggested answer & then see how she made the mistake – which is a Common Error for many Chemistry students year-after-year. [Read more…] about O Level Chemistry: Common Errors in Calculating Empirical Formula