The Mass Spectrometer

Question 1

What is a mass spectrometer?

Answer 1

Gives an accurate determination of relative atomic masses Ar

Question 2

relative atomic mass Ar

Answer 2

average mass of 1 atom divided 1/12 mass of 12C

Question 3

relative molecular mass Mr

Answer 3

average mass of molecule divided 1/12 mass of 12C

Question 4

Steps of TOF Mass Spectrometer

Answer 4

Vacuum: Apparatus kept under vacuum to prevent ions colliding with molecules of air

Ionisation: Sample dissolved in volatile solvent and forced through high voltage needle

Acceleration: Positive ions attracted towards negatively charged plate. Lighter ions achieve higher speeds

Ion Drift: Ions pass through tiny hole, forming a beam and travel along a flight tube, to a detector.

Detection: When ions arrive at detector, flight times are recorded. Positive ions pick up an electron from detector creating a current to flow.

Data Analysis: Signal passes through computer which generates a mass spectrum.

Question 5

Mass Spectra of elements

Answer 5

Detects individual ions, so different isotopes are detected separately because they have different masses. High Resolution Mass Spectrometry can measure up to five decimal places.

Question 6

Isotopes of Chlorine

Answer 6

Two Isotopes : 35 and 37

3: 1 so 75% of 35 and 25% of 37
1. (3575) + (3725) = 3550
2. 3550/100 = 35.5