plates and slit 20-5 When a magnetic sector instrument was operated with an acce
ID: 1064810 • Letter: P
Question
plates and slit 20-5 When a magnetic sector instrument was operated with an accelerating voltage of x 103 V, a field of 0.126 T was required to focus the CH4on the detector. (a) what range of field strengths would be required to scan the mass range between 16 and 250, for singly charged ions, if the accelerating voltage is held constant? (b) What range of accelerating voltages would be required to scan the mass range be tween 16 and 250, for singly charged ions, if the field strength is held constant? 20-6 calculate the accelerating voltage that would be required to direct singly chargedions of mass 10,000 through an instrument that is identical to the one described in Exam- ple 20-2 (page 503) 20-7 The ion-accelerating voltage in a particular quadrupole mass spectrometer is 5.00 V How long will it take a singly charged benzene ion to travel the length of the rod as sembly, a distance of 15.0 cm ion 20-8 on page 258 a qualitative discussion was provided that described how mass filter. would behave in the xz plane (positive dc potential plane) of a quadrupole (nega Construct a similar argument for the behavior of positive ions in the yz plane tive dc potential plane) peaks and higher resol 20.9 Why do double-focusing mass spectrometers give narrower he resolution required to resolve peaks for NT (MW tions? 00 10 Co 1Explanation / Answer
20-6)
centripetal force = magnetic force
i.e mv^2/r = qvB,,
q = charge = 1.6*10^-19 C
B = magnetic field
so as r = mv/qB here mass =m = 194 gm/mol
m = 194*10^-3/(6.023*10^23)
m = 3.22 *10^-25 kgs
speed v = q Br/m
v = 1.6 *10^-19 * 0.2* 0.101/(3.22*10^-25)
v = 1.003*10^4 m/s
from KInetic energy = PE
0.5 mv^2 = eV
V = 0.5mv^2/e
V = 0.5* 3.22 *10^-25 * 1.003*10^4 * 1.003*10^4/(1.6*10^-19)
V = 101.230 Volts
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