A researcher mixes 200 mL of hexane with an unknown amount of toluene. The resulting solution has a density of 0.85 g/mL. What is the mass of toluene added?
Q1. A researcher mixes 200 mL of hexane with an unknown amount of toluene. The resulting solution has a density of 0.85 g/mL. What is the mass of toluene added?
Answer: 30g
Explanation: Molar mass of hexane (C6H14) is 86 g/mol; hence 200 mL of hexane has a mass of approximately 86g * (200 mL / 1000 mL) = 17.2 g. Molar mass of toluene (C7H8) is 92 g/mol; hence 1 mole of toluene has a mass of 92 g. 92 g / 86 g/mol = 1.07 mol of toluene. 1.07 mol * 92 g/mol = 98 g of toluene. 200 mL * 0.85 g/mL = 170 g, leaving 170 - 17.2 - 98 = 54.8 g of toluene added. Option C is the closest.