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Calculate the excess molar volume (V_E) of a binary mixture of benzene and toluene at 298 K, given that the partial molar volumes of benzene and toluene at infinite dilution are 89.7 cm^3/mol  and  103.0 cm^3/mol,  respectively, and the molar volumes of the pure components at 298 K are 126.6 cm^3/mol and  147.1 cm^3/mol, respectively. Assume that the mixture behaves as ideal binary mixture.

Option: 1

-3.4 cm^3/mol


Option: 2

-2.6 cm^3/mol


Option: 3

2.6 cm^3/mol


Option: 4

3.4 cm^3/mol


Answers (1)

best_answer

The excess molar volume (V_E) of an ideal binary mixture is given by the equation:

V_E = V - (x_AV_A + x_BV_B)

where V is the molar volume of the mixture, V_A and V_B are the molar volumes of the pure components, and x_A and x_B are the mole fractions of the components A and B in the mixture.

Using the given data, we have:

x_A = 1/2 (since it is a binary mixture)

x_B = 1/2

V_A = 126.6 cm^3/mol
V_B = 147.1 cm^3/mol
V = x_AV_A + x_BV_B = 136.9 cm^3/mol

At infinite dilution, the partial molar volume of A and B are:

V_A\ ^\infty = 89.7 cm^3/mol
V_B\ ^\infty = 103.0 cm^3/mol

The excess molar volume can now be calculated as:
V_E = V - (x_AV_A\ ^\infty + x_BV_B\ ^\infty)\\\\ = 136.9 cm^3/mol - [1/2(89.7 cm^3/mol) + 1/2(103.0 cm^3/mol)]\\\\ = -3.4 cm^3/mol

Posted by

seema garhwal

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