H、、N、C、O、Na是初中常见的五种元素，选择适当的元素组成符合下

H、、N、C、O、Na是初中常见的五种元素，选择适当的元素组成符合下列要求的物质：

(1)焊接金属时常用作保护气的气体单质 (填化学式，下同)；

(2)焙制糕点所用发酵粉的主要成分；

(3)溶于水能使溶液温度降低的物质；

(4)炉具清洁剂中含有的碱。

答案

（1）N₂（2）NaHCO₃ （3）NH₄NO₃（4）NaOH （每空1分）

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H、、N、C、O、Na是初中常见的五种元素，选择适当的元素组成符合下

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