Question

…………… Solution is blue in color.
A. $CuS{{O}_{4}}$
B. $FeS{{O}_{4}}$
C. $ZnS{{O}_{4}}$
D. $A{{l}_{2}}{{(S{{O}_{4}})}_{3}}$

Answer 1

In aqueous solution transition metals those metals in which outermost electrons are present in d-orbital are called transition metals, form colored ions, complexes and compounds in aqueous solution. The characteristic colors are helpful to identify the composition of a sample while performing a qualitative analysis.

Complete answer: Transition metals show color due to presence of unpaired electrons in their shell which are excited to a higher level and show color. All compounds have different color and also different charge on the same compound also produces a difference in color. Out of the option given in the question copper sulphate is the only solution which shows blue color. It is due to the light energy which is used to promote or excite electrons present in the atom of the copper and when it is combined with other things like sulphate or carbonate ions etc. In solution it follows the same principle as we followed when we dissolve salt in water it dissociates salt in anion and cation or we can say in sodium and chloride ions which are not bound together any longer as they are in the crystals but surrounded by water and the water interacts with the copper ions. The color that we observe is not actually really copper sulphate; it is due to the copper ions surrounded by lots of water.

Hence we can say that option A is the correct answer.

Note: The $CuS{{O}_{4}}$ molecule consists of an ionic bond between the copper cation shown by $C{{u}^{2+}}$ and the sulfate anion shown by $S{{O}_{4}^{2-}}$. While dissolving in water like salt it also dissociates in its cation and anion and imparts color due to its positively charged copper cation.