ThermochemistryHard

Question

The enthalpy change when x g of phenol dissolves in y g of CHCl3 is given below at a certain temperature.

x Y ΔH (kcal)

0.470 120 −0.02

1.410 140 −0.03

Calculate the enthalpy of dilution per mole of phenol, when the second solution is diluted to the concentration of the first by addition of CHCl3.

Options

A.−4.0 kcal/mol
B.−2.0 kcal/mol
C.+4.0 kcal/mol
D.+2.0 kcal/mol

Solution

phOH(solution II) → phOH(solution I)

$\Delta H = \left( \frac{- 0.02}{0.47} \times 94 \right) - \left( \frac{- 0.03}{1.410} \times 94 \right) = - 2\text{ kcal/mol}$

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