[attachment id=0 msg=3713] Can you please explain how to solve this question?

Can you explain why we multiply the heat by 10 moles if there are already 2 in the equation?

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The solution of 2240 kJ is correct because the Index rxn indicates the reaction, in this case 2 H2S + 3 O2 => 2 H2O + 2 SO2  -1120 kJ/ molrxn
according Table book is Δ Η H2S = -560 kJ/mol. This value times 4 mol gives the -2240 kJ.

But in the second exercise rxn indicates the reaction of 2 C4H10 + 13 O2 => 8 CO2 + 10 H2O  -5756 kJ/ molrxn
The 580 g correspond to 10 mol Butane, and this would be 5 times -28780 kJ
Table book for 1 mol C4H10 is 2878 kJ/mol , what gives times  10 = -28780 kJ ~ 2,9 *10^4 kJ
The given answer of-5,8 *10^4 is wrong
You are right.

Quote from: gsoni on April 03, 2023, 10:19:52 PM
[attachment id=0 msg=3713] Can you please explain how to solve this question?

This is a limiting reactant question. Here both the reactants are given so check which reactant gives you minimum amount of energy.
Convert 4 moles of H₂S to kJ of energy using the ratio --- 2moles H₂S = -1120kJ of energy
Similarly convert 9 moles of O₂ to kJ of energy using ratio ---- 3 moles of O₂ = -1120kJ of energy
Check which one gives you minimum and that would be the answer.

Quote from: gsoni on April 03, 2023, 10:32:54 PM
Can you explain why we multiply the heat by 10 moles if there are already 2 in the equation?

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In this question
you can use dimensional method.
580 g of C4H10 ---> moles of C4H10 -----> kJ of energy
580 g C₄H₁₀   x    1mol C₄H₁₀/ 58 g C₄ H₁₀ x  5756 kJ of energy / 2mole C₄H₁₀
Actually 580 g has 10 moles of C₄H₁₀ then you multiply it with 5756 kJ / 2moles of C₄H₁₀