Mass Spectrometry

Question 1

What does a mass spectrometer do

Answer 1

Separates atoms and molecules according to their mass and shows the relative abundance of dif atoms and molecules present

Question 2

What state must the sample be in in a mass spectrometer and how is this achieved

Answer 2

Must be in gaseous state- done by heating the sample

Question 3

How is ionisation done

Answer 3

Beam of high energy electrons bombards the atoms/molecules of the sample, turns them into ions by knocking off one or more electrons

Question 4

What is the purpose of the vacuum in mass spectrometers

Answer 4

Allows ionised atoms/molecules to be studied without interference from atoms and molecules in the air

Question 5

What are the positive ions distinguished based on

Answer 5

Their mass-to-charge ratio

Question 6

What is mass to charge ratio

Answer 6

Ratio of the relative mass of an ion to its charge(usually charge=1)

Question 7

How does the deflection method work to separate ions

Answer 7

Electric field accelerates ions into a magnetic field which deflects the ions onto the detector. Ions with a greater m/z are deflected by a smaller amount and ions with a smaller m/z are deflected by a greater amount. So lighter and greater charge=deflected more.

Question 8

How does the time of flight method to separate ions work

Answer 8

Accelerates ions by electric field and separates them by how long it takes them to reach a detector, indicates their speed and ions with smaller mass will travel faster than those with greater mass

Question 9

What does a mass spectrometer produce and what do the lines tell us

Answer 9

A mass spectrum- height of line tells us relative abundance of that isotope while the x axis tell us mass to charge ratio

Question 10

Which line of a mass spectrum is the relative mass of the element

Answer 10

The line furthest to the right ignoring any very small lines

Question 11

What is an isotope

Answer 11

Atoms of the same element with the same number of protons but a different number of neutrons, means they have the same atomic number but dif mass numbers

Question 12

Do isotopes have the same chemical and physical properties

Answer 12

Same- chemical properties
Different- physical properties

Question 13

Relative isotopic mass

Answer 13

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

Question 14

Relative atomic mass

Answer 14

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

Question 15

Difference between relative isotopic and atomic mass

Answer 15

Isotopic is the relative mass of individual isotopes while atomic is the relative mass of atoms in an element(often contains mixture of isotopes)

Question 16

Relative molecular mass(Mr)

Answer 16

Sum of the relative atomic masses of all the atoms in its molecular formula of an element/compound

Question 17

Relative formula mass(Mr)

Answer 17

Of a compound is the sum of relative atomic masses of all the atoms in its formula

Question 18

Why do isotopes have similar chemical properties

Answer 18

Have same number of valence electrons and electronic configuration which are involved in bonding