313.03, since every molecule of lithium nitrate produces 1 lithium, where lithium sulfate consumes double, then you find that the moles of lithium sulfate are 2.27 (mass/molar mass), then multiply that by 2 (for the discrepancy in the molecule consumption/production) and then multiply that by the molar mass of lithium nitrate to find the mass of lithium nitrate needed. Hope that helped.