题目

一道关于沉淀－溶解平衡的化学题
溶液中 [Br− ] = 0.020 mol L−1 , [CrO 2− ] = 0.0030 mol L−1,在溶液中逐次加入固体硝酸银,问 Ag2CrO4(s)刚开始沉淀时 的[Br− ]
英文原题是这样的
8 In a particular solution, [Br− ] = 0.020 mol L−1 and
[CrO 2− ] = 0.0030 mol L−1. Finely-divided solid silver nitrate, AgNO3, is slowly added to the solution. What
is [Br− ] when Ag2CrO4(s) just begins to precipitate?






*A 2.1×10−8 mol L−1



B 6.0×10−8 mol L−1



C 2.7×10−7 mol L−1



D 5.2×10−13 mol L−1



E 6.4×10−4 mol L−1

提问时间：2020-10-01

答案

查表得Ksp(AgBr)=a,Ksp(Ag2CrO4)=b.
[Ag+]^2*[CrO42-(原浓度)]=b
[Ag+]*[Br-(新浓度)]=a
自己查Ksp表,带入计算