Moles

Question 1

What is relative atomic mass?

Answer 1

The relative atomic mass is the weighted average mass of
naturally occurring atoms of an element on a scale where
an atom of carbon-12 has a mass of exactly 12 units.

Question 2

What is relative isotopic mass?

Answer 2

We use the term relative isotopic mass for the mass
of a particular isotope of an element on a scale where
an atom of carbon-12 has a mass of exactly 12 units.

Question 3

What is relative molecular mass?

Answer 3

The relative molecular mass of a compound (Mr) is the
relative mass of one molecule of the compound on a
scale where the carbon-12 isotope has a mass of exactly
12 units.

Question 4

What is relative formula mass?

Answer 4

For compounds containing ions we use the term relative
formula mass. This is calculated in the same way as for
relative molecular mass.

Question 5

How to calculate Ar from mass spectra through percentage abundances?

Answer 5

■■ multiply each isotopic mass by its percentage abundance
■■ add the figures together
■■ divide by 100.

Question 6

What is molar mass?

Answer 6

We often refer to the mass of a mole of substance as its
molar mass (abbreviation M). The units of molar mass
are g mol–1

Question 7

How is mass and moles related?

Answer 7

Moles= mass/molar mass