题干

质量守恒定律是物质发生化学变化所遵循的一项基本规律。
(1)1774年,拉瓦锡将45.0份质量的氧化汞加热分解,恰好得到了41.5份质量的汞和3.5份质量的氧气,反应前后各物质的质量总和没有改变。
①该反应的化学方程式为____
②从微观角度解释反应前后各物质的质量总和没有改变的原因:____ 。
(2)为了验证质量守恒定律,甲、乙、丙三位同学各做了一个实验。
①甲同学测定的数据有:木炭和坩埚的总质量m g,木炭充分灼烧后的灰烬和坩埚的总质量n g,m和n的关系为m____n (选填“>”、“<”或“=”)。
②乙同学测定的数据有:铜片的质量x g,铜片充分加热后的质量y g,x和y的关系为x____y(选填“>”、“<”或“=”)。
③丙同学测定的数据有:铁钉、硫酸铜溶液和烧杯的总质量a g,铁钉、硫酸铜溶液充分反应后的混合物和烧杯的总质量 b g,a和b的关系为a____b(选填“>”、“<”或“=”)。
④上述实验所涉及的化学反应中,符合质量守恒定律的是____(选填“甲”、“乙”、“丙”)。

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2HgO2Hg+O2\u2191,\u5728\u5316\u5b66\u53cd\u5e94\u4e2d\uff0c\u53cd\u5e94\u524d\u540e\u539f\u5b50\u7684\u79cd\u7c7b\u6ca1\u6709\u6539\u53d8\uff0c\u6570\u76ee\u6ca1\u6709\u589e\u51cf\uff0c\u539f\u5b50\u7684\u8d28\

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