which of the following is the entropy change positive?
A. Thermal dissociation of ammonium chloride
B. Reaction between an acid and a base
C. Addition of concentrated acid to water
D. Dissolution of sodium metal in water?
please give the answer and explain.
Entropy change positive means endothermic, only one of these is endothermic, and it is a solid dissociating to a gas: positive entropy.
For this problem, thermal decomposition of the ammonium chloride would require an input of energy (endothermic) to dissociate the physical bond between HCl and Ammonia as an increase in disorder occurs with yield of more particles of product than the number of particles of reaction. However, saying that entropy means endothermic can be misleading in that there are thermochemical reactions that are exothermic with increasing entropy values. In general, combustion in presence of O2 is exothermic but is accompanied with an increase in disorder, positive entropy. Now, if this refers to requirements for achieving 'Activation Energy' for generating spontaneity, then yes, all reactions begin with an input of energy, but the net change in energy (enthalpy) may be exothermic with a positive entropy of reaction. :-)
To determine which of the given processes will result in a positive entropy change, we need to consider the nature of each process and the factors that affect entropy.
A. Thermal dissociation of ammonium chloride:
The thermal dissociation of ammonium chloride (NH4Cl) involves the breaking down of the compound into its component ions, NH4+ and Cl-. This process increases the number of particles (ions) and results in an increase in randomness or disorder. Therefore, the entropy change for this process is positive.
B. Reaction between an acid and a base:
The reaction between an acid and a base involves the formation of water and a salt. Since water is a less structured molecule compared to the molecules in the acid and base, the reaction increases the randomness of the system, resulting in a positive entropy change.
C. Addition of concentrated acid to water:
When concentrated acid is added to water, the acid molecules dissociate into ions, releasing H+ ions into the water. This process increases the disorder of the system and results in a positive entropy change.
D. Dissolution of sodium metal in water:
The dissolution of sodium metal in water involves the process of sodium atoms being surrounded by water molecules, forming hydrated sodium ions (Na+). This process results in an increase in the number of particles and randomness in the system, leading to a positive entropy change.
Based on the explanations given above, options A, B, C, and D will all result in a positive entropy change.