Molarity of solution is defined as number of moles present in one liter solution. Mathematically, it is expressed as
Molarity = [tex] \frac{\text{number of moles}}{\text{volume of solution(l)}} [/tex]
Thus, if 1 mole of solute is present in 1 liter solution, molarity of solution is 1 M.
In present case, initial conc, of solution was 1.25 M.
∴ Number of moles of co[h2o]6cl2 available initially = 1.25 mole, if the solution is 1 liter