TOF Mass Spec
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 mv^2
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 = dt
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.
kinetic energy of each ion = 1/2 mv^2
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 = dt
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.
Original post by sbscx28
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 mv^2
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 = dt
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.
kinetic energy of each ion = 1/2 mv^2
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 = dt
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.
.. and how far have you got?
Original post by sbscx28
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 mv^2
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 = dt
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.
kinetic energy of each ion = 1/2 mv^2
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 = dt
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.
Original post by charco
.. and how far have you got?
Not very :/ I know that KE is the same and I can substitute d/t over v
The two isotopes have the same kinetic energies.
Substitute
Cancel whatever else you can (they both travel the same distance), substitute whatever values you do have and rearrange for relevant t.
Substitute
Cancel whatever else you can (they both travel the same distance), substitute whatever values you do have and rearrange for relevant t.
(edited 6 years ago)
How would you get rid of t2?
Original post by charco
.. and how far have you got?
I got the answer as 3.61×10^-3 s..
Am I right?
does anyone know why 86 and 82 being used for the mass and not the mass of a singular ion in kg??
(edited 6 months ago)
Original post by gracevickers
does anyone know why 86 and 82 being used for the mass and not the mass of a singular ion in kg??
thank god there's some real human here science is literally the worst subject they change things at random and don't mention anything ugh hate it . it seems like mass values change almost every question one time is the mass of the single ion the next is the relative atomic mass of the ion the next is something else hate it .
but to answer your question from looking at the working out given they didn't bother to include d^2 so my theory is that they simplified the expression already . secondly avogardo constant is not given hence they don't wish for you to use it .
the reason for this is because avogradros constant will be on the same side of both equation hence you can cancel out avogardos constant and mass in kg is not needed as if you divide the mass is grams to kg it will also be cancelable since the mass of both ions will be divided by 1000 on both sides of the equation so the exact mass of the ion in kg is not needed aswell as avogadros constant
hope that helps
Original post by Uzanz
thank god there's some real human here science is literally the worst subject they change things at random and don't mention anything ugh hate it . it seems like mass values change almost every question one time is the mass of the single ion the next is the relative atomic mass of the ion the next is something else hate it .
but to answer your question from looking at the working out given they didn't bother to include d^2 so my theory is that they simplified the expression already . secondly avogardo constant is not given hence they don't wish for you to use it .
the reason for this is because avogradros constant will be on the same side of both equation hence you can cancel out avogardos constant and mass in kg is not needed as if you divide the mass is grams to kg it will also be cancelable since the mass of both ions will be divided by 1000 on both sides of the equation so the exact mass of the ion in kg is not needed aswell as avogadros constant
hope that helps
but to answer your question from looking at the working out given they didn't bother to include d^2 so my theory is that they simplified the expression already . secondly avogardo constant is not given hence they don't wish for you to use it .
the reason for this is because avogradros constant will be on the same side of both equation hence you can cancel out avogardos constant and mass in kg is not needed as if you divide the mass is grams to kg it will also be cancelable since the mass of both ions will be divided by 1000 on both sides of the equation so the exact mass of the ion in kg is not needed aswell as avogadros constant
hope that helps
thank you, you saved me🙏🙏🙏
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