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.

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 %


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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.

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Mole Fraction concept. You can view video lessons to learn Mole Fraction. Or if you need more Mole Fraction practice, you can also practice Mole Fraction practice problems.

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

What textbook is this problem found in?

Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition practice problems.