Chemical Calculations (1.3)

Question 1

How is the mass of an atom measured?

Answer 1

Masses of atoms are measured relative to the standard of an atom of the isotope carbon-12.

Question 2

What is the difference between Ar and Mr

Answer 2

Ar is the average mass of one atom of the atom relative to one twelfth of the mass of one atom of carbon 12 and Mr is the sum of the relative atomic masses of all atoms present in its formula

Question 3

What is the mass spectrometer used for?

Answer 3

To find the relative atomic mass of an element

Question 4

How does the mass spectrometer find the relative atomic mass ?

Answer 4

It measures the mass of each different isotope of the element
And the relative abundance of each isotope of the element

Question 5

What are the 4 main steps of the mass spectrometer?

Answer 5

Ionisation
Acceleration
Deflection
Detection
We can remember this through I ADD

Question 6

What happens at the beginning of the mass spectrometer ?

Answer 6

Vaporisation: the sample is heated and turned into a gas before it enters the spectrometer.

Question 7

What does the mass spectrometer give in formation about?

Answer 7

It will produce information about the mass and abundance of elements, compounds or mixtures.

Question 8

Wha this the second step of the mass spectrometer?

Answer 8

Ionisation:
the gaseous sample is bombarded with high energy electrons from an electron gun. This knocks electrons off one ore more electron out of the sample to form positive ions.

Mos Tod the positive ions formed will have a +1 charge as it is much more difficult to remove further electrons form an already positive ion.

Question 9

What is the third step of the mass spectrometer?

Answer 9

Acceleration: the positive ions are accelerated using an electric field and a vacuum pump.

Question 10

What is the 4 step of the mass spectrometer?

Answer 10

Deflection: the ions are deflected by a magnetic field. The amount of deflection depends on the mass and charge of the ion. Lighter ions are deflected more than the heavier ones.and ions with 2 or more + charges are deselected more than one with only one positive charge these 2 factories are combined into the m/z ratio

Question 11

What is the last step of the mass spectrometer?

Answer 11

Detection: only atoms with the correct mass charge ratio will make it through the machine
(the other ions will collide with the wall where the will pick up electrons and be neutralised)
they get removed from the mass spectrometer by the vacuum pump
The inside of the spectrometer is a vacuum so that air molecules do not interfere with the movement of the ions.

The abundance and mass/charge (m/z) ratio of the ions is read,
a mass spectrum graph is produced.

Question 12

What is an isotope ?

Answer 12

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