When 0.073 mol of aluminum sulfate are dis-solved in enough water to make 253 millilitersof solution, what is the molar concentrationof aluminum ions? Answer in units of M.
Aluminium sulfate is Al2(SO4)3 It dissociate in solution as follows Al2(SO4)3 -------------- 2Al3+(aq) + 3SO4(2-)(aq) You can see that 1 mole Al2(SO4)3 produces 2 moles Al3+ ions So 0.073 mol Al2(SO4)3 will produce (2 x 0.073) mol Al3+ ions = 0.146 moles So you have 0.146 mol of Al3+ in 253 ml Molarity = moles / L M = 0.146 mol / 0.253 L Molarity Al3+ ions = 0.58 M (2 sig figs)
