Mass spectrometry

Question 1

What information does mass spectroscopy give us about a compound?

Answer 1

Mass spectrometry can be used to determine the molecular formula of a compound.
We can find the abundance and mass of each isotope, allowing us to do this.

Question 2

How does ToF work?

Answer 2

Positive ions are accelerated by an electric field
All ions have a constant kinetic energy
If all ions have the same kinetic energy, the smaller ones move faster.
The lighter ones arrive at the detector first.
The current in the detector is proportional to the ion abundance

Question 3

KE equation + units

Answer 3

K.E. = 1/2 m v2
KE = J
m = kg
v = ms-1

Question 4

Time of flight (s) =

Answer 4

length of flight tube (m) / velocity of the particle (ms-1)

Question 5

How is a current generated?

Answer 5

The +ve ions hit the -ve charged electric plate
When they hit the detector plate, the +ve ions are discharged by gaining electrons from the plate
This generates movement of electrons and hence an electric current that is measured
The size of the current indicates abundance