将下列固体在隔绝空气的密闭容器中用酒精灯加热,在加热过程中发

将下列固体在隔绝空气的密闭容器中用酒精灯加热,在加热过程中发生了化学反应,但冷却后又凝集为原来物质的是(    )

A.碘片                B.氯化铵

C.碘化铵              D.碳酸钠

答案

B


解析:

碘片有升华的性质,但在升华过程中没发生化学变化;氯化铵受热分解成NH3和HCl气体,冷却后两气体又结合成NH4Cl;碘化铵受热也分解,但分解产物HI由于不稳定能再分解为H2和I2,冷却后得不到碘化铵;碳酸钠受热难分解。

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