You mix 34 mL of butane (C4H10, density = 0.57 g/cm3) with 48 mL of octane (C8H18, density = 0.70 g/cm3). Calculate the mass percentage (% m/m) of butane in this solution, to two significant figures.

Answer 1

To find mass % of butane, we need to know the mass of butane and the total mass of the mixture. Therefore, we also must know the mass of octane so we can add them together to get the total mass.

mass of butane: 34 ml x 0.57 g/ml = 19.38 g

mass of octane: 48 ml x 0.70 g/ml = 33.6 g

Total mass of mixture = 19.38 g + 33.6 g = 52.98 g

mass % butane = mass butane / total mass (x100%) = 36.6% = 37% (2 sig. figs.)