When excess of silver nitrate solution is added to the aqueous solution containing 0.1 mole of `CoCl_3 . xNH_3`, if 28.7g of silver chloride precipitated, what is the value of x ?

Explanation

Number of moles of AgCl precipitated = `28.7/143.5`=0.2 mole.
0.1 mole of `CoCl_3 .xNH_3` gives 0.2 mole AgCl. One mole of `CoCl_3 .xNH_3` gives 2 moles of AgCl. Thus in the complex `CoCl_2 .xNH_3`, two chloride ions satisfy only primary valence. One chloride ion satisfies both secondary valence and primary valence. Since the secondary valence of `Co^(3+)` is six and one `Cl^-` is in coordination sphere, complex possesses five `NH_3`. Thus .x. value is five.