The number of grams of Co that are in 125 Ml of 0.25 M solution is 0.87 grams
calculation
find the number of moles
moles= molarity x volume in liters
volume in liters = 125/1000 = 0.125 L
molarity = 0.25 M
moles is therefore = 0.125 x 0.25=0.0313 moles
mass = moles x molar mass
molar mass of Co= 12 +16 =28g/mol
mass is therefore = 28 g/mol x0.0313 moles= 0.87 grams