[crusader643]

Hey,

I was wondering if there is anyway to determine the colour of a precipitate without actually seeing it?
Such as when KI + Pb(NO₃)₂  PbI₂
When you mix the two colourless solutions solutions together you get yellow precipitate, is it possible to determine what colour the PbI₂ is without seeing it?

Thanks

[Borek]

is it possible to determine what colour the PbI₂ is without seeing it?

In theory - yes, it should be doable to calculate, that's what quantum mechanics is about.

In reality it is not that easy.

Besides, color of PbI₂ depends on the temperature.

[Corribus]

Measure absorption spectrum with your eyes closed, see what wavelengths are absorbed, extrapolate to color.

Although bear in mind that perceived color depends on environmental factors (ambient light, physiology of the eye, etc.) in addition to molecular properties.

[MrTeo]

In reality it is not that easy.

Right. Moreover, considering that we're talking about a solid, different crystalline forms could give different colours. This is exactly what happens when you heat HgI₂. So it also depends on the crystallization (or precipitation, which is microcrystallization) conditions.