Question

Predict the sign of the entropy change of the system for each of the following reactions.

Answer 1

Answer :

(a) The entropy change will also decreases.

(b) The entropy change will also increases.

(c) The entropy change will also decreases.

(d) The entropy change will also increases.

Explanation :

Entropy : It is defined as the measurement of randomness or disorderedness in a system.

The order of entropy will be,

As we are moving from solid state to liquid state to gaseous state, the entropy will be increases due to the increase in the disorderedness.

As we are moving from gaseous state to liquid state to solid state, the entropy will be decreases due to the decrease in the disorderedness.

(a) $N_2(g)+3H_2(g)\rightarrow 2NH_3(g)$

In this reaction, the randomness of reactant molecules are more and as we move towards the formation of product the randomness become less that means the degree of disorderedness decreases. So, the entropy change will also decreases.

(b) $CaCO_3(s)\rightarrow CaO(s)+CO_2(g)$

In this reaction, the randomness of reactant molecules are less and as we move towards the formation of product the randomness become more that means the degree of disorderedness increase. So, the entropy change will also increases.

(c) $3C_2H_2(g)\rightarrow C_6H_6(g)$

In this reaction, 3 mole of gaseous $C_2H_2$ react to give 1 mole of gaseous $C_6H_6$ that means randomness become less that means the degree of disorderedness decreases. So, the entropy change will also decreases.

(d) $Al_2O_3(s)+3H_2(g)\rightarrow 2Al(s)+3H_2O(g)$

In this reaction, the number of moles of gases are same on both side of the reaction but 1 mole of solid $Al_2O_3$ react to give 2 moles of solid aluminium that means randomness become more that means the degree of disorderedness increases. So, the entropy change will also increases.