Question

Match column 1 with column 2 for the following given.

Column 1	Column 2
$FeS{0_4}.7{H_2}O$	Green
$NiC{l_2}.4{H_2}O$	Light pink
$MnC{l_2}.4{H_2}O$	Blue
$CoC{l_2}.6{H_2}O$	Pale green
$C{u_2}C{l_2}$	Pink
Colorless

Answer 1

We must have to know that all the compounds given contain transition metals which are also known as d block elements. They are placed in the middle of s and p block elements and above f block elements. The color of any compound arises due to transitions.

Complete answer:
We will answer this question by giving correct color for the compound given in column 1 in its order only. Also the color is formed due to water crystallization. Let’s start with first which is $FeS{0_4}.7{H_2}O$ this is also known as anhydrous ferrous sulphate or ferrous sulphate heptahydrate, it is pale green in color as it lose water of crystallization. Next is $NiC{l_2}.4{H_2}O$ it is known as nickel chloride and it’s green in color. We must remember that the $MnC{l_2}.4{H_2}O$ is light pink in color since it forms d-d transitions. Next is $CoC{l_2}.6{H_2}O$, in moisture cobalt chloride changes its color from sky blue to pink, the chemical name for this compound is Cobalt chloride hexahydrate. Last is $C{u_2}C{l_2}$ it has a chemical name cupric chloride and it is colorless due to absence of paired electrons.

Note:
We have to remember that the color of the compound is due to many factors. A compound is colored if it has unpaired electrons in it; when d-d transitions occur metal will show color in them due to different transitions or movement of electrons to excited levels. We must have to remember that every element has a line emission spectrum which is defined thus color can be identified for any compound.