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B: 500g/400cm ** 3 = 1.25 g/cm ** 3
(4**2 * 3.141 * 7. 958)

That looks better now ... :)

I suggest you to check the exact number of the molecules (part a)) again.
Also part c) is still wrong ...

Tonight.
For the chemistry stuff I have to get back to Wikipedia and reread some parts.
I guess someone is already picking up my mistakes :))

Part of the price money is already yours ...
Part c) is most difficult maybe ...

Nice that you tried it, but most of it (not everything) is still wrong ... (I didn't give you more details for now not to give anybody any early hint ...)

That's the best I could do on my mobile phone :)
Will try later if no one answered

So far without any doubt your answers are the best ones (not to say: the only ones). :)

Can you check my answer in steemd?
Because the markup here is destroying my * 10**23

You can write it by using <sup>text</sup>
1023

Good that you didn't delete completely but striked out the old solution so that I can follow your solving process better. However, there are still some wrong answers ... :)

That bloody Avocado AVOGADRO .. Why isn't it a well rounded number like Pi!
Oh.. I see.. :)

EDIT: Avogadro and avocado are spellchecker mistakes on my phone.. Sorry.. Lol:)

Top and bottom of the cylinder are circle areas ... That part shouldn't be toooo difficult ...

Lol, that was funny indeed! :)