从稀盐酸、氯化铜、氢氧化钠、氧化镁、三氧化硫五种物质中，选出适当的物质，按下列要求写出化学方程式：
（1）碱与盐反应：______，
（2）酸与碱性氧化物反应：______．
（1）可溶性碱与可溶性盐若有沉淀产生则可发生复分解反应，上述五种物质中，只有氢氧化钠是碱，氯化铜是盐，两者反应生成氢氧化铜沉淀；
（2）氧化镁属于碱性氧化物，稀盐酸是酸，符合碱性氧化物与酸反应的要求．
故答案为：（1）2NaOH+CuCl2=2NaCl+Cu（OH）2↓；（2）MgO+2HCl=MgCl2+H2O．
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