relative mass

Question 1

what is the mass defect?

Answer 1

some of mass of atom is lost due to nuclear forces holding protons and neutrons

Question 2

why is carbon-12 used as the standard to measure relative atomic masses?

Answer 2

atomic weight of carbon is 12 and also, no. of proton and neutron were also 6 each which sums up to 12. So it was concluded that carbon will be the best atom for comparison of atomic masses of other elements’ atom

Also, carbon is not very abundant and does not have many isotopes

Question 3

what is the unit of relative mass

Answer 3

no units because it because it is a ratio of two masses

Question 4

relative isotopic mass definition

Answer 4

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

Question 5

relative atomic mass definition

Answer 5

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

Question 6

other way of saying relative atomic mass

Answer 6

Ar

Question 7

what does the Ar take into account?

Answer 7

• percentage abundance of each isotope

- the relative isotopic mass of each isotope

Question 8

how can the relative atomic mass be determined ?

Answer 8

using a mass spectrometer

sample is places in mass spectrometer. then its is vaporised and ionised to form positive ions
ions are accelerated. heavier ions move slower and are more difficult to deflect than lighter ions
so ions of each isotope are separated
the ions are detected on mass spectrum as a mass- to -charge ratio m/z

Question 9

mass-to-charge ratio?

Answer 9

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

Question 10

how to work out relative atomic mass?

Answer 10

Ar = sum of (isotope abundance x isotope mass number) / sum of isotope abundance