Aamc 8# 10

[BeatMCAT]

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so question is for a given magnitude of B1, the nucleus with the non zero procession frequency will be ?

a) He 4
b) O 16
c) F 19
d) 208 Pb.

I dont understand the explaination for some reason. Why is the answer C? Thanks!

 

[BilalL]

so question is for a given magnitude of B1, the nucleus with the non zero procession frequency will be ?

a) He 4
b) O 16
c) F 19
d) 208 Pb.

I dont understand the explaination for some reason. Why is the answer C? Thanks!

This passage is tricking you into forgetting your proton NMR knowledge, because essentially thats what an MRI is.

Just like electrons, protons and neutrons have spin. This allows for proton NMR and also carbon 13 NMR. Notice with Carbon 13 NMR you have an odd number for protons + neutrons, meaning that net spin is a non zero.

So for this question you also will look for the odd Mass number. So any odd Mass # or odd Atomic # will be active in NMR or MRI in this case.

 

[PingPongPro]

This was kind of a dumb question. You have to use passage info and then also deduce that you are looking for the atom with an unpaired charge. I don't remember exactly what the passage said, but the question requires you to know that positrons (the + charge of a proton) behave like electrons and have spins that pair up. The F is the one that has this non-paired charge.

 

[BeatMCAT]

Thanks!!!