Arrange the following substances in the order of increasing entropy at 25°C. a. HF(g)
b. NaF(s)
c. SiF 4(g)
d. SiH 4(g)
e. Al(s)

In solving this question it is important to note that entropy is referred to as the degree of randomness in a compound or system.

Entropy is highest in gas and lowest in solids

The order is given as:

Gas > Liquid > Solid

Another criteria is the more the elements in a compound, the more the entropy.

For example: KO3 has more entropy than KO2 due to the presence of more elements.

The last criteria is calculating their masses , the one with a greater mass has the higher entropy.

The option with the least entropy will be a solid. Al(s) and NaF(s) are both solids. NaF(s) has more elements in a compound which makes it have a higher entropy than Al(s). This means NaF(s) > Al(s).

The next to consider are the gaseous compounds which are HF(g) , SiF4(g) and SiH4(g). The least entropy will be HF(g) . This is because it has the least number of elements of the 3 compounds.

SiF4(g) and SiH4(g) have equal number of elements in a compound but the one with the highest mass is SiF4(g) because fluorine has a higher mass when compared to hydrogen. This means the compound with the highest entropy is SiF4(g).

The order of increasing entropy is given below:

Al(s) < NaF(s) < HF(g) < SiH4(g) < SiF4(g)

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