Amount of Substance

Question 1

Define relative atomic mass (Ar)

Answer 1

The average mass of an atom of an element on a scale where an atom of carbon-12 has a mass of exactly 12.

Question 2

Define relative isotopic mass

Answer 2

The mass of an atom of an isotope of an element on a scale where the mass of an atom of C-12 is exactly 12.

Question 3

Define relative molecular mass (Mr)

Answer 3

The average mass of a molecule on a scale where an atom of C-12 is exactly 12

Question 4

How do you calculate the number of particles (e.g. atoms or ions)?

Answer 4

No. of particles = no. of moles x Avogadro’s constant