A researcher mixes 150 mL of toluene with an unknown amount of hexane. The resulting solution has a density of 0.9 g/mL. What is the mass of hexane added?
Q1. A researcher mixes 150 mL of toluene with an unknown amount of hexane. The resulting solution has a density of 0.9 g/mL. What is the mass of hexane added?
Answer: 20g
Explanation: Molar mass of toluene (C7H8) is 92 g/mol; hence 150 mL of toluene has a mass of approximately 92g * (150 mL / 1000 mL) = 13.8 g. Molar mass of hexane (C6H14) is 86 g/mol; hence 1 mole of hexane has a mass of 86 g. 86 g / 92 g/mol = 0.93 mol of hexane. 0.93 mol * 86 g/mol = 79.8 g of hexane. 150 mL * 0.9 g/mL = 135 g, leaving 135 - 13.8 - 79.8 = 41.4 g of hexane added. Option C is the closest.