Question

A solution is made using 80.0 g of toluene (MM 92.13 g/mol) and 80.0 g of benzene (MM 78.11 g/mol) What is the molality of the toluene in the solution?

A. 12.8 m
B. 10.9 m
C. 6.38 m
D. 5.43 m

Answer 1

Answer:

B. 10.9 m

Explanation:

Molality of toluene = moles of toluene/mass in kilogram of benzene

Moles of toluene = mass/MW = 80/92.13 = 0.87 mole

Mass in kilogram of benzene = 80/1000 = 0.08kg

Molality of toluene = 0.87/0.08 = 10.9 m

Answer 2

The molality of the toluene will be "10.9 m".

According to the question,

→ $Molality \ of \ toluene = \frac{Moles \ of \ toluene}{Mass \ of \ benzene}$

Or,

→ $Moles \ of \ toluene = \frac{Mass}{MW}$

By substituting the values, we get

→                              $= \frac{80}{92.13}$

                               $= 0.87 \ mole$

Now,

The mass of benzene will be:

= $\frac{80}{1000}$

= $0.08 \ kg$

hence,

The molality of toluene will be:

= $\frac{0.87}{0.08}$

= $10.9 \ m$

Thus the above answer is right.

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