Our teacher told us we had to do problems on our final on Delta G and S...?
all he said is we'd have to plug in numbers from a list and solve. but im very confused.
but the numbers he gave in the example are different from my book, is there soemthing we have to do to the numbesr before plugging it in?
calculate Delta S for
N2 (g) + 3H2 (g) --> 2NH3 (g) at 298 k
he said to do products-reactants
Delta S rxn = 2 (192.5) - 1 (91.6) - 3 (130.7) = -98.7
why does my book show different numbers, did he do something with the given K?
I think your prof just slipped a line or so when looking up the numbers. I used a set of tables at home and I found, within a tenth or two, the same thing for NH3 AND for H2, but N2 was different. My table shows 191.5 for N2. Be sure you are looking under the colum for S and not for G and H.
To calculate Delta S for a reaction, you need to subtract the entropy of the reactants from the entropy of the products. The values for entropy are usually given in tables or can be calculated using various methods, such as standard entropy values or statistical thermodynamics.
In the example you provided, the reaction is N2 (g) + 3H2 (g) --> 2NH3 (g) at 298 K. The teacher used specific entropy values in the calculation, while your book might have provided different values due to slight variations in the source, rounding or different conventions.
To calculate Delta S for this reaction, you need to look up the entropy values for each species. In this case, the entropy values are:
N2 (g) = 191.6 J/mol K
H2 (g) = 130.7 J/mol K
NH3 (g) = 192.5 J/mol K
Now, you can calculate Delta S:
Delta S rxn = [2(192.5 J/mol K)] - [1(191.6 J/mol K) + 3(130.7 J/mol K)]
= 385 J/mol K - 394.7 J/mol K
= -9.7 J/mol K
The negative sign indicates a decrease in entropy for this reaction. Keep in mind that the book might use slightly different values, but the overall process and calculation remain the same. Make sure to use the correct and updated values provided in your book for accurate results.