Question

Indicate whether the entropy of the system increases or decreases for each of the following processes. Include a BRIEF explanation. Make up a process for (d) and indicate if the entropy of the system increases or decreases in that process, and provide a brief explanation as well.

a) Water boiling at 100.0°C
b) 2H₂(g) + O₂(g) ---> 2H₂O(g)
c) liquid water freezes at 0.0°C
d)
e) water vapor expanding from 1.0L of volume to 2.0L of volume
f) mixing 10mL of 90.0°C water with 10.0mL of 10°C water

Answer 1

a). When water boils, water molecules escape from the liquid state and go to gaseous/vapour state and since the vapour state has more random motion than liquid its entropy increases.

b). The reactants has total of 3 moles of gases while product has 2,since no. Of moles has decreased the entropy decreases because it has become less random.

c). When liquid water freezes it becomes ice and since ice is solid it has definite and order structure while liquid water doesn't so entropy decreases .

d). Think of rolling marbles on floor from a box... Entropy of marbles goes on increasing as long as they roll because in box they're packed in some order so are less random and while rolling they go apart and move in any direction making them more random hence increase in entropy  

e). Increase in volume leads to more randomness in case of water vapour so entropy increases because in larger volume molecules are more tended to random motion .

f). Water at 90.0^° C has molecules undergoing highly violent thermal collision and adding other water at lower temperature decreases those collisions hence resulting in decrease in entropy.