Question

A solution is made in which 55 g C8H18 and C6H6 . H18 dissolved in enough C6H6 to form 372 mL of solution. Assume the density of the solution is 0.85 g/mL. Determine the molarity of the solution and the mole fraction of C8

Answer 1

The molarity of C₈H₁₈ is 1.29 M and the mole fraction is 0.106

To find the molarity of C₈H₁₈ we use the following equation:

$M=\frac{n}{V(L)}=\frac{55 g C_8H_{18} }{0.372L}*\frac{1 mole C_8H_{18}}{114.23 g C_8H_{18}}=1.29 M$

Now to find the mole fraction of C₈H₁₈, we have to find the grams of C₆H₆

We know that we have 55 g grams of C₈H₁₈, and that the total volume is 372 mL, from density we can find that the total mass of the solution is 0.85g/mL * 372mL = 316.2 g.

Now we know that the mass of C₆H₆ is 316.2 g - 55 g = 261.2 g and the mole fraction is:

$X_{C_8H_{18} }=\frac{n_{C_8H_{18} }}{n_{C_8H_{18} }+_{C_6H_{6} }} =\frac{(55/114.23)}{(55/114.23)+(316.2/78.11)}=0.106$

Have a nice day!

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