Question

PH相等的HCl溶液和HAc溶液等体积混合后?PH值是变大,还是变小,还是不变?

Answer 1

不变.

设原来pH=2.

________________HA====H+ + A-

起始浓度：_______c____0____0

平衡浓度：____c-0.01_0.01_0.01

K=(0.01*0.01)/(c-0.01)

________________HA====H+ + A-

起始浓度：______c/2__0.005___0

平衡浓度：_____c/2-x_0.005+x__x

K=(0.005+x)x/(c/2-x)

(0.005+x)x/(c/2-x)=(0.01*0.01)/(c-0.01)

经近似处理,得x=0.005,x+0.005=0.01.

即氢离子浓度没有变化.