Reviewed CSCA Chemistry question · Easy

在恒容密闭容器中发生反应：A(g) + 2B(g) ⇌ 2C(g)。起始时充入1 mol A和2 mol B，平衡时测得C的物质的量为1.0 mol。则A的转化率为多少？

25%
50%
75%
100%

Show the answer and explanation

Correct answer

B. 50%

Principle or equation

转化率 = 已转化的物质的量 / 起始物质的量 × 100%。

Why this answer is correct

设A转化的物质的量为x mol，则生成C为2x mol。平衡时C为1.0 mol，所以2x = 1.0，x = 0.5 mol。A的转化率 = 0.5 / 1 × 100% = 50%。

Example

若反应为2A(g) + B(g) ⇌ 2C(g)，起始A为2 mol，平衡C为1.2 mol，则A转化1.2 mol，转化率60%。

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