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质量是500g的铁壶内装有2kg15℃的水，若把这壶水加热到100℃，共需要吸收多少热量？如果这些热量全部由木炭燃烧来提供，需要完全燃烧多少克木炭？ {（木炭的热值是3.4×107J/kg）（C铁=0.46×103J（kg·℃）}

A.4×107J/kg）（C铁=0.46×103J（kg·℃）}

【参考答案】

733550J；约21.6g
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一台太阳能热水器装满水后，水的质量是80kg。使这些水的温度从20℃升高70℃ 需要吸收________J的热量。若这些热量由燃烧天然气来提供，则至少应完全燃烧_______m3的天然气。 （C水=4.2×103J／（kg·℃）天燃气的热值为8×107J／m3）
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