1.3

Question 1

Define relative atomic mass

Mass spectroscopy

Answer 1

The average mass of one atom of the element relative to 1/12 of the mass of one atom of carbon-12

Question 2

Define relative isotopic mass

Answer 2

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

Question 3

Define relative formula mass

Answer 3

The average mass of a molecule relative to 1/12 of the mass of one atom of carbon-12

Question 4

What does a mass spectrometer do?

Answer 4

Calculates the masses of isotopes of an element along with their relative abundances

Question 5

What are the 5 stages of mass spectroscopy?

Answer 5

1. Vaporisation
2. Ionisation
3. Acceleration
4. Deflection
5. Detection

Question 6

What happens in the vaporisation stage?

Answer 6

The sample is heated and turned into a gas before it enters the spectrometer

Question 7

What happens in the ionisation stage?

Answer 7

The gaseous sample is bombarded with high energy electrons, which forms positive ions

Question 8

What happens in the acceleration stage?

Answer 8

The positive ions are accelerated through an electric field

Question 9

What happens in the deflection stage?

Answer 9

The ions are deflected by a magnetic field.

Question 10

What affects the amount of deflection?

Answer 10

The mass and charge of the ion (Lighter ions are deflected more than heavier ones)

Question 11

What happens in the detection stage?

Answer 11

Some ions pass through a slit and are detected by the detector. Only those ions of the correct mass/charge ratio will be able to pass through the slit.

Question 12

What conditions are the inside of the spectrometer? Why?

Answer 12

The inside of the spectrometer is under vacuum conditions so that air molecules do not interfere with the movement of the ions

Question 13

What formula is used to calculate Ar from the results of the spectrometer?

Answer 13

∑ isotope mass x isotope abundance / 100.

Question 14

How do you calculate the relative formula mass?

Moles and empirical formula

Answer 14

Add up the Ar for each atom in the compound/molecule

Question 15

Define a mole

Answer 15

The amount of substance that contains as many particles as there are atoms in 12g of carbon-12 (Avogadro’s constant)

Question 16

What is molar mass?

Answer 16

The mass of one mole of substance (same as the Ar or Mr)

Question 17

What is an empirical formula?

Answer 17

The simplest formula, giving us the proportions of elements present in a compound in its simplest ratio - but not the actual number of atoms of each element

Question 18

What is a molecular formula?

Answer 18

The actual number of elements of each element that are present in the molecule.

Question 19

How do you calculate empirical formula?

Answer 19

1. Calculate the moles of each element (Mass/Mr)
   2.Divide the answers by the smallest answer
2. Use these answers as a ratio to write the formula

Question 20

Define hydrated salts and water of crystalisation

Water of crystalisation

Answer 20

Hydrated salts have water molecules (Water of crystallisation) incorporated into their structures

Question 21

How do you calculate the water of crystalisation?

Answer 21

1. Mass of hydrated salt - Mass of anhydrous salt = mass of water in the hydrate
2. Find the moles of anhydrous salt and the moles of water
3. Calculate the ratio

Question 22

How do you calculate what mass of a product is made?

Answer 22

1. Calculate the moles of reactant
2. Find the molar ratio using the numbers balancing the equation
3. Mass = moles x Mr