下列物质化学式，书写正确的是（ ）
A．FeSO4（硫酸铁）
B．HCl（氯化氢）
C．Mg2O2（氧化镁）
D．AgCl2（氯化银）
A、FeSO4（硫酸铁），化学式表示该物质是硫酸亚铁；书写错误．
B、HCl（氯化氢），化学式书写正确．
C、Mg2O2（氧化镁），化学式应为MgO，书写错误．
D、AgCl2（氯化银）化学式应为AgCl，书写错误．
故选 B．
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