I have the infamous \"Test Tube Mystery\" lab practical coming up next week. The

Question

I have the infamous "Test Tube Mystery" lab practical coming up next week. The twelve solutions that will be provided are:

HCl

Cu(NO3)2

NiCl2

H2SO4

Ba(NO3)2

FeCl3

NH4OH

AgNO3

K2CrO4

NaOH

Pb(NO3)2

Na2CO3

I am not allowed any litmus paper or any additional chemicals. What is the best strategy for this? My teacher said I should have 5 of the twelve right off the bat:

Cu(NO3)2: blue

K2CrO4: yellow

NiCl2: green

NH4: smells strongly

...and there is supposed to be one more that can be identified by color. Which is it? FeCl3?

What is the best strategy for these particular chemicals?

Thanks so much!

Explanation / Answer

Ok so CuSO4 is blue

NiCl2 is green

K2CrO4 is yellow

NH3 smells really bad like the guy above said

mix AgNO3 and K2CrO4 (the yellow) and you get an almost blood red solution

Pb(NO3)3 and K2CrO4 gives a really bright yellow precipitate

NH3 and CuSO4 makes a royal blue color

Na2CO3 and CuSO4 makes a blue precipitate and fizzes

NaOH and CuSO4 make a blue precipitate but DOES NOT FIZZ

HCl and CuSO4 turns yellow/greenish

AlCl3 and K2CrO4 turns a little darker of a yellow, but so does HCl and K2CrO4

as for NaCH3COO I am still looking but I am starting to think that sodium acetate plus NaOH will form a precipitate due to the common ion effect, but I am not sure.

Source:

AP chem

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