Question

Why was carbon-12 preferred over oxygen-16 to be chosen as the standard reference for measuring atomic masses? [2 MARKS]

Answer 1

Each point : 1 Mark

1. Oxygen is a mixture of O-16 , O-17 and O-18 isotopes, which gives the average mass if oxygen is taken as the standard.

2. C-12 is the most abundant isotope of carbon which constitutes 98.9% of available isotopes of carbon.
So it was better to choose Carbon-12 isotope as the standard.