For which pair is the magnetic moment $\mu = \sqrt{15} \ BM$ correct?

Indicate the types of isomerism exhibited by the following complexes and draw the structures for these isomers:
$(i)$ $K[Cr(H_2O)_2(C_2O_4)_2]$
$(ii)$ $[Co(en)_3]Cl_3$
$(iii)$ $[Co(NH_3)_5(NO_2)](NO_3)_2$
$(iv)$ $[Pt(NH_3)(H_2O)Cl_2]$

Which of the following complexes is paramagnetic?

The following complexes are given:
$1$. $\text{trans}-[Co(NH_3)_4Cl_2]^+$
$2$. $\text{cis}-[Co(NH_3)_2(en)_2]^{3+}$
$3$. $\text{trans}-[Co(NH_3)_2(en)_2]^{3+}$
$4$. $[NiCl_4]^{2-}$
$5$. $[TiF_6]^{2-}$
$6$. $[CoF_6]^{3-}$
Choose the correct code:

$A$ reaction of cobalt $(III)$ chloride and ethylenediamine in a $1:2$ mole ratio generates two isomeric products $A$ (violet coloured) and $B$ (green coloured). $A$ can show optical activity,but $B$ is optically inactive. What type of isomers do $A$ and $B$ represent?

$26.7 \ g$ of a compound with the formula $PtCl_2Br_2 \cdot 6H_2O$ is taken for analysis. This compound exhibits stereoisomerism,and a total of $3$ stereoisomers exist. Find the loss in mass (in $g$) when the given amount of the compound is treated with concentrated $H_2SO_4$. (Molar mass: $PtCl_2Br_2 \cdot 6H_2O = 534 \ g \ mol^{-1}$)