The transition metal complex with the highest value of crystal field splitting $(\Delta_{0})$ is ........ .

Which among the following complexes is associated with the maximum wavelength of light absorbed?

The total number of unpaired electrons present in the $d^3$, $d^4$ (low spin), $d^5$ (high spin), $d^6$ (high spin), and $d^7$ (low spin) octahedral complex systems is . . . . . . .

$CuSO_4 \cdot 5 H_2O$ is blue in colour while $CuSO_4$ is colourless. Why?

Arrange the following Cobalt complexes in the order of increasing Crystal Field Stabilization Energy $(CFSE)$ value.
Complexes: $[CoF_{6}]^{3-}, [Co(H_{2}O)_{6}]^{2+}, [Co(NH_{3})_{6}]^{3+}$ and $[Co(en)_{3}]^{3+}$
$A: [CoF_{6}]^{3-}, B: [Co(H_{2}O)_{6}]^{2+}, C: [Co(NH_{3})_{6}]^{3+}, D: [Co(en)_{3}]^{3+}$
Choose the correct option:

The number of unpaired $d$-electrons in $[Co(H_2O)_6]^{3+}$ is $\qquad$