Question

Which of the following reactions have a positive ΔSrxn? Check all that apply.

A(g) +B(g) -----> 3C(g)
A(g)+ B(g)------> C(g)
2A (g) +2B (g)-----> 3C(g)
A(s)+B(s)------> C(g)



I picked the first one and it marked me wrong.
Please help(:

Answer 1

1 and 4 should do it.
1, I suspect for the same reason you picked it. 4 because A and B are SOLIDS; therefore, converting them to a gas certainly would be a positive dS.

Answer 2

Yes it is correct! Thanks :)

Answer 3

I had similar problem, except correct choices were 2A(g)+B(s)->3C(g) and A(g)+B(g)->3C. Just wanted to thank Dr.Bob for explaining how it actually works.

Answer 4

Which reactions have a positive Δ𝑆rxn?

2A(g)+2B(g)⟶3C(g)

2A(g)+3B(g)⟶4C(g)

2A(g)+B(g)⟶4C(g)

A(s)+B(s)⟶C(g)