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TOF Mass Sprectrometry question

My teacher went through it however, one of the calculations was inconsistent with her answer so I need a way to answer the question:

In the TOF mass spectrometer, a germanium ion reaches the detector in 4.654 x 10 to the power of -6 s.
The kinetic energy of this ion is 2.438 x 10 to the power of -15 J.
The length of the flight tube is 96.00cm.

The kinetic energy of an ion is given by the equation KE=1/2mv2.

where
m=mass/kg
v=speed/ms-1

The Avogadro constant L = 6.022x10 to the power of 23 mol-1.

Use this information to calculate the mass, in g, of one mole of these germanium ions. Use your answer to state the mass number of this germanium ion.
Reply 1
Avatar for saura
saura
9
might be wrong but this is what i would do

i need to find out velocity so i would do distance divided by time. However i had to convert the distance into metres first. When i did distance divide time i got 20627.41728 as my velocity. I then arranged the KE equation as mass = 2KE divided by velocity squared. using this arranged equation I did 4.876 x 10 to the -5 divided by 425490343.5 (i did the squaring on the velocity and multiplying the KE by 2 beforehand). This got me 1.145971953 x 10 to the -13. I now multiply by 1000 and then multiply by avogadros constant to get 6.9 x 10 to the 13 (3 s.f)

now this might not be right or it might be right I just did this for practice
Yh I got this as well... but I doubted myself because I thought it was too big an answer
isnt that wrong tho the velocity is meant to be 206274.1727 not 20627.41727
Original post by omegabravo
Yh I got this as well... but I doubted myself because I thought it was too big an answer

isnt that wrong tho your meant to get what i put below as the velocity
Original post by Daniel Tamosev
My teacher went through it however, one of the calculations was inconsistent with her answer so I need a way to answer the question:

In the TOF mass spectrometer, a germanium ion reaches the detector in 4.654 x 10 to the power of -6 s.
The kinetic energy of this ion is 2.438 x 10 to the power of -15 J.
The length of the flight tube is 96.00cm.

The kinetic energy of an ion is given by the equation KE=1/2mv2.

where
m=mass/kg
v=speed/ms-1

The Avogadro constant L = 6.022x10 to the power of 23 mol-1.

Use this information to calculate the mass, in g, of one mole of these germanium ions. Use your answer to state the mass number of this germanium ion.

K.E = 0.5 *m * v2 = 2.438 x 10-15 J

Time taken = 4.654 x 10-6 s
Distance = 96.00cm = 0.96 m

Velocity = Distance/time = 0.96/4.654 x 10-6 s = 206274.1728 ms-1
Velocity squared = 4.255 x 1010

m = 2 * 2.438 x 10-15/4.255 x 1010
m = 1.146 x 10-25 kg

m per mol = 1.146 x 10-25 x 6.0223 x 1023 = 0.0690 kg

mass of ion per mol = 69.0 g
yeah thats what me and my mates got and then as the mr we got 69
i have done this question somewhere before which paper was it in?
Original post by idkkkkkk
i have done this question somewhere before which paper was it in?

No idea... i don't even remember replying to this post lol
Reply 9
Avatar for JayEoly
JayEoly
4
Original post by idkkkkkk
i have done this question somewhere before which paper was it in?

its from the 2019 chem AS paper 1
OML, this is the first time i prolly got a 5 marker right, i just checked it against the answer that someone gave, AND AAHHHH I GOT ITTT!!!

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