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# i need a genius? watch

1. if you have 1.5cm cubed of 0.2 molarity iron chloride, why is it if you mix it with 0.5 water you get 0.15 molarity. and if u 1.25 water with 0.75 fecl3 you get 0.075 and so on.
2. 0.0003moles of FeCl in the first
if you add 0.5cm^3 water you get 2cm^3 of 0.15M

yes that's correct. What's the problem? You use the equation:

moles = concentration*volume
where the volume is in dm^3 (to convert from cm^3, divide by 1000)
3. im assuming you mean 0.5 cm³ water....

originally: n = cv = 0.2 * 0.0015 = 0.0003 moles FeCl3

0.5 cm³ water is added, but the moles of iron chloride stays the same, so
c = n/v = 0.0003/(0.0015 + 0.0005) = 0.15 M
4. if the solid was pure: you would take the required mass of solid (i believe the rmm of FeCl3 is 162.5). so 162.5g of the pure solid dissolved in 5l of pure water would make a 0.2M solution. you can then use that to make the other solutions
5. how does "elpaw" make me polish? it could be "the paw" in spanish.

as for my knowledge, i did Alevel Chemistry.
6. ok i thought you meant - my name "elpaw"
7. yeah, 4 As
8. Someone's been deleting posts...
9. (Original post by mik1a)
Someone's been deleting posts...
either that or elpaws goin crazy..
10. (Original post by ShOcKzZ)
either that or elpaws goin crazy..
there were posts there a minute ago
11. (Original post by ShOcKzZ)
either that or elpaws goin crazy..
Good point. Eplaw's finally lost it.
12. (Original post by mik1a)
Good point. Eplaw's finally lost it.
Lol...someone's framing Elpaw...

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