The heat of fusion of dichloromethane (CH2Cl2) is 6.2 kJ/mol.
Calculate the change in entropy Δs when 345 g of dichloromethane freezes at -95.1 °C.
Be sure your answer contains a unit symbol and the correct number of significant digits.

Answer : The entropy change of the dichloromethane is 142 J/K

Explanation :

To calculate the number of moles, we use the equation:

Given mass of dichloromethane = 345 g

Molar mass of dichloromethane = 84.93 g/mol

Putting values in above equation, we get:

To calculate the entropy change for different phase at same temperature, we use the equation:

where,  

= Entropy change  = ?

n = moles of dichloromethane = 4.06 moles

= enthalpy of fusion = 6.2 kJ/mol = 6200 J/mol   (Conversion factor:  1 kJ = 1000 J)

T = temperature of the system =

Putting values in above equation, we get:

Hence, the entropy change of the dichloromethane is 142 J/K

it should be p1 v1 = p2 v2