【实验一】制备氮化铝

【资料1】实验室常用饱和亚硝酸钠与氯化铵溶液反应制取纯净的氮气。

有关反应的化学方程式为：

NaNO₂+NH₄Cl    NaCl+N₂↑+2H₂O（此反应是放热反应）；

Al₂O₃+3C+N₂2AlN+3CO

试回答：

|﹣$\frac{1}{2}$|的相反数是（　　）

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