90.0g of MgCI2 was placed in 50.0cm3 of water to give a saturated solubility of the salt is 8.0 mol dm3 at the same temperature, what is the mass of the salt left undissolved at the given temperature? (Mg = 24, Cl = 35.5)
A. 52.0g B. 58.5g C. 85.5g D. 88.5g
Correct Answer: A
Explanation
Molar mass of MgCl2 = 95g The solubility of MgCl2 is 8.0/dm3 1 dm3 = 1000cm3 Solubility of g/cm3 8 x 95 → 1000cm3 x → 50 x = (50)/(1000) x (8 x 95) / (1) = 38g Mass of the salt left undissolved = 90 - 38 = 52.0g
