Which of the following is expected to have zero entropy?
i. n₂(g) at 273 k
ii. sio₂(s, amorphous) at 0 k
iii. nacl(s) perfectly ordered crystal at 25 k
iv. na(s) perfectly ordered crystal at 0 k

IV

Explanation:

Entropy is a measure of the degree of disorderliness in a particular molecule. What we are saying is that randomization plays an important role in the quest for determining a molecule at a point of disorderliness.

Now let us look at the answer choices.

N2 is a gas and is expected to have a high amount of degree of disorderliness.

SiO2 although is at the absolute zero temperature which is supposed to necessitate a low entropy amount, the fact that it is not ordered I.e amorphous confers a degree of disorderliness in its molecule.

NaCl although perfectly ordered is not at the absolute zero and hence cannot exhibit the needed degree of disorderliness.

Na is our answer choice because it meets the two criteria needed for zero entropy. Firstly, it is of considerable orderliness and hence, entropy isn’t expected in its molecule. Also, it has no disturbance in the case of temperature as it is at absolute zero.

6.4 cm (max) - 25 cm (min)