Question

What is the change in entropy of the lead when 2.0 kg of molten lead at its melting point temperature solidifies.

Answer 1

Answer: The change in entropy of the lead when 2.0 kg of molten lead at its melting point temperature solidifies is 20 cal/K.

Explanation:

$Pb(l)\rightleftharpoons Pb(s)$

$\Delta S=\frac{q}{T}$

${\text{Change in entropy}}=\frac{heat}{Temperature}$

T is the temperature at which the process is carried out, here the temperature is constant, 327.5°C = $(273+327.5)K=600.5K$ ,because only phase change occurs.

q =  heat given in the process = $m\times L_f$

m = mass of lead = 2.0 kg

$L_f$ = latent heat of fusion of lead =  5.9 kcal/kg

$\Delta S=\frac{2kg\times 5.9kcal/kg}{600.5K}$

$\Delta S=0.02 kcal/K=20cal/K$

Thus the change in entropy of the lead when 2.0 kg of molten lead at its melting point temperature solidifies is 20 cal/K.