99毫升0.1mol/L盐酸,n(H+)=0.099L×0.1mol/L=0.0099mol,101毫升0.05mol/L氢氧化钡溶液,n(OH-)=0.101L×0.05mol/L×2=0.0101mol,反应后溶液的体积为99mL+101mL=200mL=0.2L,则反应后c(OH-)=
=1×10-3mol/L,Kw=c(H+)×c(OH-),c(H+)=0.0101mol?0.0099mol 0.2L
=1×10-11,pH=-lgc(H+),pH=11,1×10?14
1×10?3
故选C.