The enthalpy of atomization of carbon and hydrogen are q1 and q2 respectively. If q3 is the B.E. of C−H bond, then ∆H of the following reaction is: C(s) + 2H2(g) → CH4(g)
Correct answer: D. q1 + 4q2 − 4q3
- A. 4q3 − q1 − 2q2
- B. q1 + q2 − q3
- C. q1 + 2q2 − 4q3
- D. q1 + 4q2 − 4q3
Explanation
C(s) + 2H2(g) → CH4(g); ∆H = ? C(s) → C(g); ∆H1 = q1 H2(g) → 2H(g); ∆H2 = 2q2 ∆H = q1 + 4q2 − 4q3
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About Bond Energy
Bond energy is the energy needed to break one mole of a particular covalent bond in gaseous molecules, while bond formation releases energy. Reaction enthalpy is estimated by subtracting the total energy of bonds formed from bonds broken, with attention to average bond energies and their limitations for specific molecules.
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