In: Chemistry
Which of the following reactions have a positive ?Srxn? Check all that apply.
2A(g) + 2B(g) -->5C(g)
2A(g) +3 B(s) --> 4C(g)
A(s) + 2B(g) --> C(g)
A(s) + B(g) -->2C(g)
is
the entropy change in a reactant from reactant to product side. The
change in the standard molar entropy
of a reaction can be found by the difference between the sum of
the molar entropies of the products and the sum of the molar
entropies of the reactants.
In the reactaions given by you, the no of moles in the reactant and product sides decide the nature of entropy change in the reactions, i.e., whether the entropy change is positive or negative in the reaction.
=
positive/negative if
=(
No of
moles of products -
No of moles of
reactants)= positive/negative
Now, for the reactions given in the questions:
2A(g) + 2B(g) -->5C(g)
= 5- (2+2)=
+1. Thus,
is
positive for the reaction.
2A(g) +3 B(s) --> 4C(g)
= 4- (2+3)=
-1. Thus,
is
negative for the reaction.
A(s) + 2B(g) --> C(g)
= 1- (1+2)=
-2. Thus,
is
negative for the reaction.
A(s) + B(g) -->2C(g)
= 2- (1+1)=
0. Thus,
is
zero for the reaction, i.e., there is no net entropy
change.