Find the increase in the water's entropy.

Question

Suppose that by stirring 495 g of water you are able to increase its temperature from 19.0° C to 21.0° C. Find the increase in the water's entropy.

answer in J/K

Answer 1

Take Specific Heat (or C_p) of Water as 4.1813 Kilojoules-Per-Kilogram-Dot-Kelvin

and write 19°Celsius and 21°Celsius as 292.15 Kelvin and 294.15 Kelvin.

Equate Heat Transfer Q to mC_p(T₂ − T₁₎ which evaluates to

(0.495 kg)(4.1813 kJ/[kg • K]){294.15 − 292.15} K or 4.139487 kJ.

Then set down ΔS_net as mC_p • ln[T₂/T₁] + {Q/T₂} equal here to

(0.495 kg)(4.1813 kJ/[kg • K]) • ln[294.15 K/292.15 K] + {4.139487 kJ/294.15 K}

which reduces to 0.02819347552 kJ/K (or 28.19347552 J/K).