（3分）有氯化镁、硫酸铜、氯化钡三瓶白色粉末，用水就可将它们鉴别出来，首先鉴别出的物质是____________，在剩余两种物质的鉴别操作过程中发生反应的化学方程式是                  。

The Grammer-Translation Method believes that grammar is the ______ of language, and language materials are arranged according to the grammar system.