Which one of the following processes produces a decrease in the entropy of the system?
a. boiling water to form steam
b. dissolution of solid kcl in water
c. mixing of two gases into one container
d. freezing water to form ice
e. melting ice to form water.

Explanation:

Entropy -

In a system, the randomness is measured by the term entropy .

Randomness basically refers as a form of energy that can not be used for any work.

The change in entropy is given by amount heat per change in temperature.

When solid is converted to liquid or gas entropy increases,

As the molecules in solid state are tightly packed and has more force of attraction between the molecules, but as it is converted to liquid or gas, the force of attraction between the molecule decreases and hence entropy increases.

So,

The particles of the substance , if are tightly held by strong force of attraction will decrease the entropy ,

And

If the particles are loosely held , the entropy will increase , i.e. , when gas is converted to liquid or solid .

A. boiling water to form steam ,

change of state from liquid to gas ,

and , hence entropy increases .

B. dissolution of solid KCl in water  ,

the number of particles increases ,

and hence , entropy increases .

C. mixing of two gases into one container  ,

the number of particles increases ,

and hence , entropy increases .

D. freezing water to form ice  ,

change of state from liquid to solid ,

and hence , entropy decreases .

E. melting ice to form water .

change of solid to liquid ,

and hence , entropy increases .

nacl or sodium chloride is an ionic compound. this is because an ionic compound pertains to a compound that consists of positively and negatively charged ions. in this case, na (sodium) has a tendency to lose one electron when it reacts with with other atoms, so the resulting sodium ion contains 11 protons and 10 electrons, thus making it positively charged (na+), when chlorine reacts, it usually gains one electron to form an ion called chloride, thus making it negatively charged ( since the ions are oppositely charged, they attract.