Excess aqueous $\mathrm{AgNO}{}_3$ is added to a solution of $[\mathrm{Co}(\mathrm{NH}{}_3){}_5\mathrm{Cl}]\mathrm{Cl}{}_2$. The number of moles of $\mathrm{AgCl}$ precipitated per mole of the complex is

Only the two chloride ions outside the square brackets are free ions. The chloride inside the coordination sphere is bound to cobalt and is not precipitated. Hence 2 mol of $\mathrm{AgCl}$ form per mole of complex.