How Does a Mass Spectrometer Calculate the Path of Protein Fragments?

[mntnhiker8]

Homework Statement

A mass spectrometer is designed to separate protein fragments. The fragments are ionized by removing a single electron and then enter a 0.80 T uniform magnetic field at a speed of 2.3*10^5 m/s
If a fragment has a mass that is 85 times the mass of the proton, what will be the distance between the points where the ion enters and exits the magnetic field?

Homework Equations

The Attempt at a Solution

I used m=(qBr)/V also tried r= (2mv/2qB^2)^.5

and then multipid r *2 to get d? Nothing is working. The value m I'm using is 1.4*10^-25, B=.8, q=1.6*10^-19, v=2.3*10^-5?

Help.

 

[anathema]

Dear forum post author,

Thank you for your question. It seems like you are on the right track with using the equation m=(qBr)/V to solve this problem. However, there may be a few errors in the values you are using.

Firstly, the mass of the protein fragment should be given in kilograms, not in arbitrary units like 1.4*10^-25. So you may need to convert the given mass of 85 times the mass of the proton into kilograms.

Secondly, the velocity should also be given in meters per second, not in an arbitrary unit like 2.3*10^-5. So you may need to convert the given speed of 2.3*10^5 m/s into meters per second.

Once you have converted the values to the correct units, you can plug them into the equation m=(qBr)/V and solve for the radius r. Then, as you mentioned, you can multiply the radius by 2 to get the distance between the points where the ion enters and exits the magnetic field.

I hope this helps. If you are still having trouble, please provide your updated calculations and we can work through them together.

 

[ogb p]

I understand the importance of accurately solving problems and finding the correct solution. Based on the information provided, I can suggest the following steps to solve this problem:

1. First, let's clarify the given values:
- Mass of the fragment = 85 times the mass of the proton = 85 * 1.67 * 10^-27 kg ≈ 1.42 * 10^-25 kg
- Magnetic field strength = 0.80 T
- Velocity of the fragment = 2.3 * 10^5 m/s

2. Now, let's use the equation m = (qBr)/V to calculate the charge (q) of the fragment. We know the mass (m), magnetic field strength (B) and velocity (V), so we can rearrange the equation to solve for q.
q = mV/(Br) = (1.42 * 10^-25 kg * 2.3 * 10^5 m/s)/(0.80 T * r)

3. We also know that the charge of the fragment (q) is equal to the charge of an electron (e) multiplied by the number of electrons removed (n). In this case, only one electron is removed, so n = 1. Therefore, we can write:
q = ne = (1)(1.6 * 10^-19 C) = 1.6 * 10^-19 C

4. Now, we can substitute this value of q in the previous equation and solve for r:
r = (mV)/(Be) = (1.42 * 10^-25 kg * 2.3 * 10^5 m/s)/(0.80 T * 1.6 * 10^-19 C) ≈ 0.11 m

5. Since we want the distance between the points where the ion enters and exits the magnetic field, we can multiply r by 2 to get the total distance:
d = 2r ≈ 0.22 m

Therefore, the distance between the points where the ion enters and exits the magnetic field is approximately 0.22 meters. I hope this helps!