Relative Mass

Question 1

Relative mass

Answer 1

Masses of atoms compared to carbon 12

Question 2

Relative atomic mass (Ar)

Answer 2

The average mass of an atom of an element compared to a carbon 12 atom

Question 3

Relative isotopic mass

Answer 3

The mass of an atom of an isotope of an element compared to a carbon 12 atom

Question 4

Relative molecular mass (relative formula mass) (Mr)

Answer 4

The average mass of a molecule or formula unit compared to a carbon 12 atom

Question 5

How are relative masses measured

Answer 5

Mass spectrometer

Question 6

What are the 4 things that happen within a mass spectrometer

Answer 6

1.Vaporisation, 2.Ionisation, 3.Acceleration, and 4.Detection

Question 7

Vaporisation - mass spectrometer

Answer 7

The sample is turned into gas using an electrical heater

Question 8

Ionisation - mass spectrometer

Answer 8

The gas particles are bombarded with high energy electrons to ionise them, electrons are then knocked off the particles leaving positive ions

Question 9

Acceleration - mass spectrometer

Answer 9

The positive ions are accelerated by an electric field

Question 10

Detection - mass spectrometer

Answer 10

The time taken for the positive ions to reach the detector is measured, this depends on ions mass and charge, light highly charged ions will be detected first, while heavier ions with smaller charge take longer

Question 11

A mass spectrum graph

Answer 11

Y-axis gives the abundance of ions, as percentage, x-axis units are given as mass/charge ration, or simply relative mass

Question 12

Ar using mass spectrum

Answer 12

=(Σ (isotopic mass * relative abundance)) / Σ (relative abundance)

Question 13

Mg has three isotopes, 79% Mg24, 10% Mg25, and 11% Mg26, work out the Ar

Answer 13

~24.3

Question 14

114.0 of Ne20, 0.2 of Ne21, and 11.2 of Ne22, work out the % Ar for Neon 20

Answer 14

~90.9%

Question 15

120.8 of Cu63 and 54.0 of Cu65, work out the Ar of copper

Answer 15

~63.6