# Mass-to-Charge Ratio of an Ion in Mass Spectrometer

• camel-man
In summary, the conversation discusses finding the mass to charge ratio of an ion based on given values for fields and velocities. The equations used are v = E/B and m = qrB/V. The attempt at a solution yielded a value for v that was off when plugged into the equation for m. However, when the given numbers are used in the expression for m/q, the resulting value is close to the known value for a specific particle.
camel-man

## Homework Statement

Consider fields of 1.4e5 N/C and 2.7 T within a velocity selector. If the charge then exits and encounters a field of 1.4 T and radius of 2.4 mm within the mass spectrometer, what would be the mass to charge ratio of this ion?

## Homework Equations

v = E/B
m = qrB/V[/B]

q = 1.6 x 10 ^-19C
r = 2.4 x 10^-3 m
B = 1.4 T

## The Attempt at a Solution

I got 51851 m/s for v

and my answer came out way off when I plugged it in for m.

I have the answer but when I try to do it myself. I get the wrong answer.

Last edited by a moderator:
The exercise asks for m/q, not for m. What did you get ?
And what exactly do you mean when you say 'I get the wrong answer' ?

By the way: you got 5.2 x 104 m/s, not 51851 m/s : you can't achieve five digit accuracy when all you're given is two digit numbers! But v wasn't wanted.
(However, when you work out this exercise with the given numbers in the expression for m/q, you do end up to within 1 promille of m/q of a known particle...what a coincidence!)

## 1. What is the Mass-to-Charge Ratio (m/z) in a Mass Spectrometer?

The Mass-to-Charge Ratio, also known as m/z, is a measurement used in mass spectrometry to determine the mass of an ion relative to its charge. It is calculated by dividing the mass of the ion by its charge. This ratio is important because it allows for the identification and analysis of different ions in a sample.

## 2. How is the Mass-to-Charge Ratio measured in a Mass Spectrometer?

In a mass spectrometer, the mass-to-charge ratio is measured by first ionizing a sample, which creates positively charged ions. These ions are then accelerated through an electric field, causing them to separate based on their masses and charges. The ions are then detected and their m/z values are recorded.

## 3. What is the relationship between Mass-to-Charge Ratio and Ion Mass in a Mass Spectrometer?

The Mass-to-Charge Ratio is directly related to the mass of an ion in a mass spectrometer. As the mass of an ion increases, its m/z value will also increase. This is because the charge on the ion remains constant, so a heavier ion will have a larger mass-to-charge ratio than a lighter ion.

## 4. How is the Mass-to-Charge Ratio used for identification in Mass Spectrometry?

The Mass-to-Charge Ratio is an important factor in the identification of ions in mass spectrometry. Each type of molecule has a unique m/z value, so by comparing the m/z values of the ions in a sample to a database, scientists can determine the molecular composition of the sample. This is useful in fields such as chemistry, biology, and forensics.

## 5. What are the limitations of using Mass-to-Charge Ratio in Mass Spectrometry?

While the Mass-to-Charge Ratio is a valuable tool in mass spectrometry, there are some limitations to its use. One limitation is that it cannot distinguish between ions with the same m/z value but different molecular structures. Additionally, the accuracy of the m/z measurement can be affected by factors such as instrument resolution and sample contamination. Therefore, it is important to use other techniques in conjunction with mass spectrometry for a more comprehensive analysis.

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