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ToF Mass Spectroscopy

2017 Paper One

Question Four
If you haven't gone through the question/paper, click the direct link below, and have a go...

AQA A-level CHEMISTRY Paper 1 Inorganic and Physical ChemistryTuesday 13 June 2017


An 8-mark, 4-part question



The relative atomic mass of titanium is 47.8 to one decimal place.
 
Use the m/z value in the table = 46


Mass of one atom of Ti-49:


Don't forget to convert to kilograms.
 

The kinetic energy is a constant as is the length of the tube

Here's one way (a little rearranging is required)...

the length of the tube is the same for both ions, so...
The kinetic energy is a constant as is the length of the tube for both ions. L, of course, is also a constant - we can cancel them out.

The time of flight for the ion is:

Note: there are other ways to solve this.

This question proved a step too far for a lot of students with many gaining no marks. The manipulation is fairly straightforward - I would brush up on maths skills if you found this difficult
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