Which one of the following reactions would you expect to have highest ΔS°?

Answer
A. C2H2(g) + 5/2O2(g) → 2CO2(g) + H2O(g)
B. C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(g)
C. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
D. C2H6(g) + 7/2O2(g) → 2CO2(g) + 3H2O(g)

Increase in dS in gases can be estimated from the number of mols difference between products and reactants.

A. mols on left = 3.5....right..3. decrease in S
B. left mols = 4; ....right...4 no change in S.
C. left 3...right 3 no change in S
D. left 4.5.....right 5 higher number of mols on right. higher dS for reaction.

Hmm, let me think about this one. Ah, I got it! So, we're looking for the reaction with the highest ΔS°, which represents the change in entropy. Now, entropy is a measure of disorder or randomness, so we want to find the reaction that has the most chaos going on.

So, let's see. In option A, we have C2H2 reacting with 5/2O2 to give 2CO2 and H2O. Option B involves C2H4 reacting with 3O2 to give 2CO2 and 2H2O. Option C has CH4 reacting with 2O2 to give CO2 and 2H2O. Lastly, option D involves C2H6 reacting with 7/2O2 to give 2CO2 and 3H2O.

Now, notice that the number of moles of gas on the reactant side is different from the number of moles of gas on the product side in each reaction. And remember, gases are more disorderly than liquids or solids, like a party where everyone is just floating around, right?

So, taking that into account, the reaction that has the most change in entropy would be the one that goes from fewer moles to more moles of gas. If you follow that logic, you'll find that option D, C2H6 reacting with 7/2O2 to give 2CO2 and 3H2O, has the highest ΔS°. It's like a chaotic party with lots of gas molecules dancing around.

To determine which reaction would have the highest ΔS° (change in entropy), we need to analyze the number of moles of gas on both the reactant and product side of each reaction. Generally, an increase in the number of moles of gas will result in a higher entropy.

Let's calculate the moles of gas on both sides of each reaction:

A. C2H2(g) + 5/2O2(g) → 2CO2(g) + H2O(g)
Reactants: 2 moles of gas
Products: 3 moles of gas

B. C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(g)
Reactants: 3 moles of gas
Products: 4 moles of gas

C. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
Reactants: 3 moles of gas
Products: 3 moles of gas

D. C2H6(g) + 7/2O2(g) → 2CO2(g) + 3H2O(g)
Reactants: 5 moles of gas
Products: 6.5 moles of gas

Based on our calculations:

A. ΔS° = Products - Reactants = (3 moles) - (2 moles) = 1 mole of gas
B. ΔS° = Products - Reactants = (4 moles) - (3 moles) = 1 mole of gas
C. ΔS° = Products - Reactants = (3 moles) - (3 moles) = 0 moles of gas
D. ΔS° = Products - Reactants = (6.5 moles) - (5 moles) = 1.5 moles of gas

From the calculations, we can see that reaction D (C2H6(g) + 7/2O2(g) → 2CO2(g) + 3H2O(g)) has the highest ΔS°, with 1.5 moles of gas. Therefore, the answer is D.

To determine which reaction would have the highest ΔS°, we need to look at the change in entropy (∆S°) for each reaction. Entropy is a measure of the disorder or randomness of a system.

To calculate the change in entropy (∆S°) for a reaction, we can use the formula:

∆S° = ΣnS°(products) - ΣmS°(reactants)

where n and m represent the stoichiometric coefficients of the products and reactants, respectively, and S° represents the standard entropy values for the substances involved.

Now let's calculate the change in entropy for each reaction:

A. C2H2(g) + 5/2O2(g) → 2CO2(g) + H2O(g)
∆S° = 2S°(CO2) + S°(H2O) - [S°(C2H2) + (5/2)S°(O2)]

B. C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(g)
∆S° = 2S°(CO2) + 2S°(H2O) - [S°(C2H4) + 3S°(O2)]

C. CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
∆S° = S°(CO2) + 2S°(H2O) - [S°(CH4) + 2S°(O2)]

D. C2H6(g) + 7/2O2(g) → 2CO2(g) + 3H2O(g)
∆S° = 2S°(CO2) + 3S°(H2O) - [S°(C2H6) + (7/2)S°(O2)]

To determine which reaction would have the highest ΔS°, we need to compare the magnitudes of the change in entropy values. In this case, we don't need to calculate the exact values of ΔS°. Instead, we can consider the number of moles of gaseous species produced and consumed in each reaction.

Looking at the stoichiometric coefficients, we can see that reaction B produces the highest number of moles of gaseous species (2 CO2 + 2 H2O) compared to the other reactions. Producing more moles of gaseous species generally leads to a higher change in entropy. Therefore, reaction B (C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(g)) would be expected to have the highest ΔS° among the given options.