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Topic: which 0.1M solution is colourless?  (Read 2311 times)

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Offline helenee

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which 0.1M solution is colourless?
« on: April 19, 2019, 05:27:03 AM »
A 0.1 M solution of which of the following is colorless?

A) MgCl2
B) Ni(NO3)2
C) Na2CrO4
D) KMnO4
E) CuSO4

I did choose A, but I just guessed. If I didn't have any background knowledge of these, is there a way I could have still chosen the right answer (without having to be lucky)?

Offline chenbeier

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Re: which 0.1M solution is colourless?
« Reply #1 on: April 19, 2019, 07:08:25 AM »
No, you have to learn the colour of cathions and anions. Ni(H2O)62+ green, CrO42- yellow, MnO4- purple, Cu(H2O)42+ blue. The other all colourless Mg2+, Cl-, NO3-, Na+, K+ and SO42-.

Offline mjc123

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Re: which 0.1M solution is colourless?
« Reply #2 on: April 20, 2019, 05:20:51 PM »
The coloured ones contain transition metal ions.

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