Chromate ions

[Ice-cream]

Can any1 tell me if CrO4 (2-) is the formula for a chromate ion? Also, does any1 know the wavelength of it or the colour of light it absorbs? (I've looked on the web and there are diff. answers...) Can some1 plz help me?

[BenSon]

<wrong answer>

[neo007]

Yea, you're right, chromate ion is CrO4 (2-).

Just a random equilibrium between chromate and dichromate ion:

H2O + Cr2O7(2-) 2CrO4(2-) + 2H+

[Ice-cream]

does any1 know anything about the wavelength or the colour of the light absorbed by chromate ions? coz i've been to lots of websites and they all give diff. answers. i think the colour of chromate ions is yellow, so that means it absorbs the purple light (complementary colours)...but i'm not sure if that's right. does any1 agree with me?