Atomic structure and amount of substance

Question 1

Define atomic number

Answer 1

Number of protons in the nucleus of an atom

Question 2

Define mass number

Answer 2

The total number of protons plus neutrons in the nucleus

Question 3

Define isotope

Answer 3

Atoms with the same number of protons but a different number of neutrons

Question 4

What does a mass spectrometer help determine?

Answer 4

The mass of separate atoms (or molecules)

Question 5

What is the job of the vacuum in a flight mass spectrometer?

Answer 5

The whole apparatus is kept under a high vacuum to prevent the ions that are produced from colliding with molecules from the air

Question 6

What happens in the ionisation stage in a flight mass spectrometer?

Answer 6

An electron gun bombards the atom with a beam of electrons to knock off an electron from the atom’s outer shell to produce a singulary positive charged ion

Question 7

What happens in the acceleration stage in a flight mass spectrometer?

Answer 7

The positive ions are attracted towards a negatively charged plate and accelerate towards it.
Lighter ions and more highly charged ions achieve a higher speed

Question 8

What happens in the ion drift stage in a flight mass spectrometer?

Answer 8

The ions pass through a hole in the negatively charged plate, forming a beam and travel along the flight tube to a detector.

Question 9

What happens at the detection stage in a flight mass spectrometer?

Answer 9

When the ions with the same charge arrive at the detector, the lighter ones are first as they have the higher velocities.
The flight times are recorded
The positive ions pick up an electron from the detector, which causes a current flow

Question 10

What happens at the data analysis stage in the flight mass spectrometer?

Answer 10

The signal from the detector is passed to a computer which generates a mass spectrum

Question 11

Define ionisation energy

Answer 11

The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous materials

Question 12

What is ionisation energy a measure of?

Answer 12

The amount of energy needed to remove electrons from atoms

Question 13

Define Avagadro’s number

Answer 13

The total number of particles in a mole of substance

Question 14

Define a Mole

Answer 14

A quantity of a substance that contains the avagadro number of particles

Question 15

What do solutions consist of?

Answer 15

A solvent with a solute dissolved in it

Question 16

What does concentration tell you?

Answer 16

How much solute is present in a known volume of solution

Question 17

What is the ideal gas equation?

Answer 17

pV=nRT

Question 18

What is pressure measured in?

Answer 18

Pa

Question 19

What is volume measured in?

Answer 19

m^3

Question 20

What is temperature measured in?

Answer 20

K

Question 21

Define atom economy

Answer 21

A reaction is found directly from the balanced equation. It is theoretical rather than practical

Question 22

How do you work out % atom economy?

Answer 22

(Mass of desired product/Total mass of reactants)x100

Question 23

What does % atom economy tell us?

Answer 23

How many atoms must be wasted in a reaction

Question 24

What does the percentage yield of a chemical reaction tell us?

Answer 24

The practical efficiency of the process, how much is lost by: the practical process of obtaining a product, as a result of reactions that don’t go into completion