What is the secondary valence of $Co^{3+}$ ion according to Werner's theory in $[Co(NH_3)_4 Cl_2]^+$?

Some salts,although containing two different metallic elements,give a test for only one of them in solution. Such salts are:

Which of the following coordination compounds will yield the maximum amount of $AgCl$ upon reaction with an excess of $AgNO_3$ for $1 \ mol$ of the compound?

What is a coordination compound?

In $Fe_{x}[Fe_{y}(CN)_6]_3$,$x$ and $y$ respectively are:

On treatment of $10 \ mL$ of $1 \ M$ solution of the complex $CrCl_3 \cdot 6H_2O$ with excess of $AgNO_3$,$4.305 \ g$ of $AgCl$ was obtained. The complex is