Question

【大一分析化学疑难】请高手指教一下第三题的5/6/7

Answer 1

5.（NH4+）*（OH-）/(NH3)=Ka

x*(x+10^-3)/0.1=4.74

x=0.688

OH-=0.689

pH=13.8

6.H3PO4:pKa1=2.12 pKa2=7.20 pKa3=12.36

c*Ka3=0.1*10^-12.36约等于Kw

c/Ka2>>10

(H+)=根号（10^-7.2*(10^-12.36*0.1+10^-14)/0.1）=3.01*10^-10

pH=9.52

7.c*Ka2=0.5*10^-7.20>>10Kw

c/Ka1=0.5/10^-2.12=65.9>10

(H+)=根号（Ka1*Ka2）=2.188*10^-5

pH=4.66