2.2 Relative Mass

Question 1

Define ‘relative isotopic mass’

Answer 1

Mass of an isotope relative to 1/12th of the mass of an atom of carbon-12

Question 2

Define ‘relative atomic mass’

Answer 2

Weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12

Question 3

What can mass spectrometry be used for? (2)

Answer 3

• Masses and relative abundances of the isotope

- Calculation of the Ar of an element from the relative abundances of its isotopes

Question 4

Are relative molecular mass and relative formula mass the same? When are the terms used

Answer 4

Yes
BUT Molecular mass for simple structures
Formula mass for giant structures

Question 5

How does a mass spectrometer work?

Answer 5

(1) Sample placed in (2) Vaporised then ionised (3) Ions are accelerated (heavier ions=slower) (4 )Detected as a mass:charge ratio

Question 6

When the ion reaches the detector in the mass spectrometer it adds to the signal. What does a large signal show?

Answer 6

A greater abundance of ions

Question 7

What is the equation for the mass:charge ratio?

Answer 7

m/z=relative mass of ion/relative charge on ion