已知1 g氢气完全燃烧生成水蒸气时放出热量121 kJ，且氧气中1 mol O=O键完全断 裂时吸收热量496 kJ，氢气中1 mol H―H键断裂时吸收热量为436 kJ，求水蒸气中1 mol H―O键形成时放出热量
| A．463kJ | B．557 kJ | C． 486kJ | D．188 kJ |
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