# Paper 1 set 2 specimen paper Question 11.2

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#1
Does anyone know how to answer this question because I really don't have any idea

A sample of the element Q consists of several isotopes. All of the Q+ ions in the sample of Q that has been ionised in a TOF mass spectrometer have the same kinetic energy.

kinetic energy of each ion = 1 2 mv2

where m is the mass, in kg, of one ion of an isotope and v is the velocity of an ion in m s–1

v = d t

where d is the length, in m, of the flight tube and t is the time taken, in s, for an ion to reach the detector The time of flight of a 82Q+ ion is 1.243 × 10–5 s.

Calculate the time of flight of the 86Q+ ion?
0
3 years ago
#2
(Original post by JacobV98)
Does anyone know how to answer this question because I really don't have any idea

A sample of the element Q consists of several isotopes. All of the Q+ ions in the sample of Q that has been ionised in a TOF mass spectrometer have the same kinetic energy.

kinetic energy of each ion = 1 2 mv2

where m is the mass, in kg, of one ion of an isotope and v is the velocity of an ion in m s–1

v = d t

where d is the length, in m, of the flight tube and t is the time taken, in s, for an ion to reach the detector The time of flight of a 82Q+ ion is 1.243 × 10–5 s.

Calculate the time of flight of the 86Q+ ion?
Put v = d/t into 0.5mv2

Sub in the numbers for the 82 ion to form equation 1.
Sub in the numbers for the 86 ion to form equation 2.
Equate the equations.

The d2 will cancel out.

Re-arrange for t2 and take the square root.

Alternatively, you could give KE a value, such as 1, since both ions will have the same amount of kinetic energy. From this, you'd be able to work out d and then the time for the 86 ion, however, this is more work.
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#3
How do you put v=d/t into 0.5mv ?
0
3 years ago
#4
(Original post by JacobV98)
How do you put v=d/t into 0.5mv ?
KE = 0.5mv2

v = d/t

KE = 0.5m(d/t)2

KE = 0.5m(d2/t2)
1
#5
Okay, Thank you, that make sense.
0
3 years ago
#6
i am still stuck could you please provide some more details on how to do it?
0
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