[bookworm]

After 5ml of nickel salt solution was pipette and add with about 1ml of dilute hydrochloric acid followed by diluting with 100ml of water, it was brought to heat to 70degree C - 80degree C.

1) why must the solution be kept below 80degree C during precipitation stage ?

my ans :is to remove the ethanol from the solution and to ensure that the solution does not contain ethanol during precipitation??

2) what are the main sources of error and how do i minimize them ?

my ans: the main source of error is the purity of the precipitate as Zn2+, Mn2+ interfere the precipitate because their hydroxides are formed under the ammoniacal conditions used

[Borek]

1) why must the solution be kept below 80degree C during precipitation stage ?

my ans :is to remove the ethanol from the solution and to ensure that the solution does not contain ethanol during precipitation??

Hm, if you want to remove ethanol it will be wise to heat sample to boliling, not to keep it at lower temp.

[bookworm]

hmm.. then is it if solution is boiled above 80 degree C, evaporation will take place quickly and much solution may evaporate away which result in loss of precipitate. The concentration of nickel obtained will be lower. If solution is kept below 80 degree C, evaporation will take place more slowly and lesser solution will be evaporated away and more precipitate will be obtained. The concentration of nickel obtain will be higher

[Borek]

much solution may evaporate away which result in loss of precipitate

Why do think there will be loss in the precipitate?

[bookworm]

it has exceeded it's boiling point ?

[Borek]

Boiling point of precipitate? Precipitate is solid, before starting to boil it has to melt first. I doubt it happens below 100 deg C.

[bookworm]

is it becos we added dilute hydrochloric acid into nickel salt solution that's why we  have to boil it below 80 degree C?

[joevan]

then wat's is the answer??

[Borek]

I am afraid we have to decide what is the question first. I have no idea what your question relates to.

[joevan]

i've done the experiment of gravimetric determination of nickel..during the precipitation process,the temperature of the solution must be maintained at about 60-80celsius..why?