# Mechanical Engineering - Thermodynamics - Discussion

Discussion Forum : Thermodynamics - Section 2 (Q.No. 13)

13.

The entropy of water at 0°C is assumed to be

Discussion:

27 comments Page 1 of 3.
Sivaramakrishnaiah said:
5 years ago

Entropy zero only at absolute temperature 0K.

Vilas s h said:
6 years ago

At 0°c water will freeze but a moment of particles are there when particles are moving how the entropy is zero. At 0k there is no particles movement, means no moment zero entropy.

Aditya loachab said:
6 years ago

According to the third law of thermodynamics, entropy remains until temperature 0K because some molecular momentum is there till 0Kelvin.

Manoj sutahr said:
6 years ago

Yes, it should be absolute Zero temp that is 0K.

(1)

Sohan said:
6 years ago

For 0K, entropy is zero for perfectly crystalline substance, but 0 K is unachieveable and absolute entropy is not measurable, hence we take triple point of water arbitrarily as 0 entropy.

Shahid said:
7 years ago

Entropy should be zero at 0° K, but in case of water 0 entropy is assumed at 0° celcius.

Virendra said:
7 years ago

It should be 0 K, and not 0°.

Ananda said:
7 years ago

S=mcln(t2/t1).

Here t1=t2=273 kelvin,

So ln(273/273)=ln(1)= 0,

Hence S=0.

Here t1=t2=273 kelvin,

So ln(273/273)=ln(1)= 0,

Hence S=0.

Muhammed aslam said:
7 years ago

Actually, entropy has some value at 0 degree centigarade. We cannot achieve zero entropy (according to 3rd law). But for ease of calculation we assume entropy is zero for water at zero degree celcius. Steam table is based on this concept. However absolute value of entropy or enthalpy is not important at all. Always we consider change in entropy on process.

Akash said:
8 years ago

When 0k Entropy is 0 but it only applicable for pure crystal substance so water is not pure Crystalline substance.

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