- #1

- 654

- 2

## Homework Statement

Find entropy change of total system of heatbath + water when water is placed in heat bath from 20 C to 50 C, then 50C to 80C. assume equilibrium is reached first in both cases.

water = 1000g , C = 4.2J/C/G

## The Attempt at a Solution

the entropy for water S

_{w}= CdT / T + Cdt / T , where first integral from 293K to 323K, second from 323K to 353K.

bath entropy S

_{b}= -C(353 - 293) / 353

S

_{w}=780.4

S

_{b}=-713.8

S-total = 66.6 J/K

but ans is 35.6J/K .

apparently, the 2 step process of heating should get me a smaller entropy change, but the value i calculated 66.6 is around the same as if i did a 1 step heating from 20 to 80 straight.

so where did i go wrong? thanks!