Find ΔS∘ for the reaction between nitrogen gas and fluorine gas that forms nitrogen trifluoride gas. 12N2(g)+32F2(g)→NF3(g)

Question

Standard Entropies for Selected Substances at 25 ∘C

Substance S∘(J/mol⋅K)
N(g) 153.3
N2(g) 191.6
F(g) 158.75
F2(g) 202.79
NF3(g) 260.8

Answer 1

I'm not sure what the equation is that you've included.  How about this?

1/2 N₂(g) + 3/2 F₂(g) ==>NF₃

∆S = ∑n∆S_products - ∑n∆S_reactants

∆S = 260.8 - [(1/2 x 191.6) + (3/2 x 202.79) = 260.8 - (95.8 + 304.19)

∆S = 260.8 - 399.99

∆S = -139.2 J/K  (note the negative sign)