[INeedSerotonin]

Which of these can be successfully separated through magnetic separation?

A) Fe and Al
B) Fe and Si
C) Mg and Cu
D) Mg and Co
E) Fe and Ni

I don't know. This exercise doesn't make sense to me. Aren't all of these metals? Shouldn't all of them be dragged by the magnet? Perhaps this was a badly elaborated exercise?

Could you guys give me a hint here?

Thanks

[AWK]

But some metals show magnetic properties

[INeedSerotonin]

A) Fe and Al <--- Fe is ferromagnetic; Al is paragmanetic
B) Fe and Si <--- Fe is ferromagnetic; Si is... I don't know
C) Mg and Cu <--- Magnesium is paramagnetic; Cu is diamagnetic
D) Mg and Co <---- Magnesium is paramagnetic; Cobalt is ferromagnetic
E) Fe and Ni <--- both are ferromagnetic

Perhaps the answer should be (A), (C), and (D)? Because a paramagnetic substance is very weak; and a ferromagnetic substance is strongly attracted to a magnet.

When I found this exercise, the website said that the answer is (E), which is what left me confused. How could we separate Fe and Ni through magnetic separation if both are ferromagnetic?

[AWK]

Magnetic separation of nickel and iron is possible between temperatures 358 and 770°C. But this is not a question for beginner chemists.

[Enthalpy]

In ordinary industrial processes, only ferromagnetic (and ferrimagnetic ones, if you want to distinguish) substances are separated from the others.

If the question was "Which two metals can be separated from nonmagnetic ones" then E is the only good answer. I dislike this wording.

Besides the exercise, you should keep in mind that ferromagnetism is not an atomic property. It's a molecular one. Nickel makes austenitic stainless steel nonmagnetic. CrO₂ is a permanent magnet. Some polymers without any metal atom are ferromagnetic.

And also: once I could attract brass with a permanent magnet. Brass was a small rod, well round, rolling freely on a table, hence very sensitive to forces. Unexpected from Cu-Zn, both diamagnetic. Possibly that brass included some Fe or Ni from the ore or from recycling, and they precipitated during the production.

[INeedSerotonin]

Thank you, guys! I take note of everything you guys say. I'm learning a lot here!