Question

what is entropy? what happens to the entropy nacl crystals are dissolved in water? what is the condition for the spontaneity at constant temperature and pressure in terms of entropy chage ​

Answer 1

Entropy is a measure of the degree of randomness or disorder of a system. Entropy is an easy concept to understand when thinking about everyday situations.

When NaCl dissolves in water the strong ionic bonds are broken (requiring heat energy) and the ions interact with water molecules (releasing heat energy). The solution of NaCl in water has much less order than the pure water and the crystalline salt. Entropy increases every time a solute dissolves in a solvent.

Entropy is a state function, and freezing is the opposite of melting. At −10.00 °C spontaneous, +0.7 J/K; at +10.00 °C nonspontaneous, −0.9 J/K.