Question

The color of light absorbed by an aqueous solution of `CuSO_"4"` is??

Answer 1

Well, red, but I don't see how you would know that without doing the experiment or googling the compound.

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`"Cu"^(2+)` is blue in aqueous solution. `"CuSO"_4` has a `lambda_(max)` of about `"635 nm"` (red). It reflects the color blue, so it absorbs mostly red light, the complementary color.