Question

What is the change in entropy when 2.5 mole of water is heated from 27⁰C to 87⁰C ? Assume that the heat capacity is constant. (Cp,m (H2O) = 4.2 J/g-K ln (1.2) = 0.18)

• A. 16.6 J/K
• B. 9 J/K
• C. 34.02 J/K
• D. 1.89 J/K

Answer 1

Answer: (C)

34.02 J/K

Answer 2

$\Delta$S = nC p, m In $\frac{T_{2}}{T_{1}}$= 2.5 × 18 × 4.2 In $\left( \frac{360}{300} \right)$= 34.02 J/K