Problem: A solution is prepared by mixing 25 mL pentane (C5H12, d = 0.63 g/cm3) with 45 mL hexane (C6H14, d = 0.66 g/cm3). Assuming that the volumes add on mixing, calculate the mass percent, mole fraction, molality, and molarity of the pentane.

🤓 Based on our data, we think this question is relevant for Professor Bindell's class at UCF.

FREE Expert Solution

We are asked to calculate the mass percent, mole fraction, molality, and molarity of the pentane.


Step 1. Calculate mass of each

Recall: 

density = massvolumemass C5H12 =25 mL × 1 cm31  mL ×0.63 g1 cm3 = 15.75 gmass C6H14 =45 mL × 1 cm31  mL ×0.66 g1 cm3 = 29.7 g


Step 2. Calculate moles each

Molar mass C5H12 = 72.17 g/mol

Molar mass C6H14 = 86.20 g/mol


15.75 g C5H12  × 1 mol C5H12 72.17  g C5H12  = 0.22  mol C5H12 29.7 g C6H14  × 1 mol C6H14 76.20  g C6H14   = 0.39 mol C6H14 


Step 3. Mass percent pentane

Mass % = mass solutemass solution ×100Mass % C5H12= 15.75 g15.75 g+ 29.7 g ×100Mass % C5H12= 15.75 g45.45 g ×100

Mass % C5H12 = 34.65 %


View Complete Written Solution
Problem Details

A solution is prepared by mixing 25 mL pentane (C5H12, d = 0.63 g/cm3) with 45 mL hexane (C6H14, d = 0.66 g/cm3). Assuming that the volumes add on mixing, calculate the mass percent, mole fraction, molality, and molarity of the pentane.