On the assumption that copper– nickel alloys are random mixtures of copper and nickel atoms, calculate the mass of copper which, when mixed with 100 g of nickel, causes an increase in entropy of 15 j/k. the gram atomic weights of cu and ni are, respectively, 63.55 and 58.69.

65.14 g

Explanation:

The change in the entropy of two ,metals on mixing is

Here, R is real gas constant, n_{cu} is the number of moles of the copper, and n_{Ni} is the number of moles of nickel

Thus the number of moles of Nickel is

=1.7 moles

now put n_{Ni} = 1.7  ΔS= 15,

R= 8.314 and solve

On solving the number of moles of copper in the mixture

n_cu= 1.025

Thus the mass of copper is = n_cu×M_cu = 1.025×63.55 =  65.14 g

Therefore the required mass is =  65.14 g

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