$A$ metal complex with a formula $MCl_4 \cdot 3NH_3$ is involved in $sp^3d^2$ hybridisation. It upon reaction with excess of $AgNO_3$ solution gives '$x$' moles of $AgCl$. Consider '$x$' is equal to the number of lone pairs of electron present in the central atom of $BrF_5$. Then the number of geometrical isomers exhibited by the complex is $............$

$CoSO_{4}Cl \cdot 5NH_{3}$ exists in two isomeric forms '$A$' and '$B$'. Isomer '$A$' reacts with $AgNO_{3}$ to give white precipitate,but does not react with $BaCl_{2}$. Isomer '$B$' gives white precipitate with $BaCl_{2}$ but does not react with $AgNO_{3}$. Answer the following questions.
$(i)$ Identify '$A$' and '$B$' and write their structural formulas.
$(ii)$ Name the type of isomerism involved.
$(iii)$ Give the $IUPAC$ name of '$A$' and '$B$.'

Which of the following compounds does not exhibit paramagnetism?

Which of the following is not correctly matched?

Which of the following compounds has a zero magnetic moment?

Assertion : $[Fe(CN)_6]^{3-}$ is weakly paramagnetic while $[Fe(CN)_6]^{4-}$ is diamagnetic.
Reason : $[Fe(CN)_6]^{3-}$ has $+3$ oxidation state while $[Fe(CN)_6]^{4-}$ has $+2$ oxidation state.