question_answer

Give reasons: (a) Neither \[q\] nor \[w\] is a state function but \[q+w\] is a state function. (b) The dissolution of ammonium chloride in water is endothermic still it dissolves in water. (c) A real crystal has more entropy than an ideal crystal.

Answer:

                (a) \[q+w=\Delta U\]. As \[\Delta U\] is a state function, hence \[q+w\] is a state function. (b) On dissolution, entropy increases, i.e., \[\Delta S\] is +ve. Though \[\Delta H\] is +ve but if \[T\Delta S>\Delta H,\]  then according to the equation, \[\Delta G=\Delta H-T\Delta S,\,\Delta G\]will be -ve. Hence, the process is spontaneous. (c) A real crystal has some disorder due to presence of defects whereas ideal crystal has no disorder. Hence, a real crystal has more entropy than ideal crystal.