AP Chemistryhardmcq1 pt
Estimate ΔH for H₂ + Cl₂ → 2HCl using bond enthalpies. (H–H 436, Cl–Cl 243, H–Cl 431 kJ/mol)
A.−183 kJ
B.+183 kJ
C.−248 kJ
D.+679 kJ
Explanation
Core Concept
Bonds broken: 436 + 243 = 679 kJ. Bonds formed: 2 × 431 = 862 kJ. ΔH = 679 − 862 = −183 kJ — exothermic, as expected for HCl formation.
Correct Answer
A−183 kJ
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