在盛有足量A的容积可变的密闭容器中加入了B，发生反应A+2B=4C+D，在一定温度，压强下达到平衡。

平衡时C的物质的量与B的物质的量的变化关系如图。（C的物质的量为Y轴，B的物质的量为X轴，两夹角成45度）下列说法正确的是:
A平衡时B的转化率为百分之五十。
B若再加入B，则再次达到平衡时正逆反应速率均曾大
C若保持压强一定，再加入B，则反应体系中气体的密度减少
为什么要选那个

选C

A 错误 设平衡时B的 转化率是x，则有
1-x=2x
解得x=1/3
B 错误 只要容器内的压强，温度不变，最终达到平衡时，反应速率就是不变的。

A 再看看别人怎么说的。

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