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If hydrogen were used as a fuel, it could be burned
Chapter 9, Problem 105E(choose chapter or problem)
If hydrogen were used as a fuel, it could be burned according to this reaction:
Use average bond energies to calculate rxn for this reaction and also for the combustion of methane (CH4). Which fuel yields more energy per mole? Per gram?
Questions & Answers
QUESTION:
If hydrogen were used as a fuel, it could be burned according to this reaction:
Use average bond energies to calculate rxn for this reaction and also for the combustion of methane (CH4). Which fuel yields more energy per mole? Per gram?
ANSWER:Solution 105E Step 1 of 4 For the reaction Thus we can see that at the end of this reaction one HH bond and 1/2 O=O bond are broken and 2 bonds OH are formed.We have to remember that when a reaction happens, we have to spend energy to break bonds (positive H ), while broken bonds release energy (negative H) Since For H-H H = 436 kJ/mol For O=O H = 498 kJ/mol Thus H broken bonds= (H H-H)+ 1/2 (H O=O)= 685 kJ/mol For O-H H = -464 kJ/mol Thus H formed bonds= 2(H O-H)= -928 kJ/mol Since H RXN (H broken bonds) + (H formed bonds) H RXN (685 kJ/mol) + (- 928 kJ/mol)= -243 kJ/mol This means that 1 mol of H re2ases 243 kJ.