`pH=2`
`=>[H^+]=0,01`
`=>n_(HCl)=n_(H^+)=0,01.0,1=0,001(mol)`
`pH=12`
`=>[OH^-]=0,01`
`=>n_(NaOH)=n_(OH^-)=0,01.0,2=0,002(mol)`
`H^(+)+OH^(-)->H_2O`
`n_(OH^- (dư))=0,001(mol)`
`=>[OH^-]=\frac{0,001}{0,3}=1/(300)M`
`pH=14+log([OH^-])=11,52`
`2,`
`n_(H_2SO_4)=0,1.0,05=0,005(mol)`
`=>n_(H^+)=0,005.2=0,01(mol)`
`n_(NaOH)=0,4.0,05=0,02(mol)`
`n_(OH^-)=0,02(mol)`
`H^(+)+OH^(-)->H_2O`
`n_(OH^- (dư))=0,01(mol)`
`[OH^-]=\frac{0,01}{0,5}=0,02M`
`pH=14+log([OH^-])=12,30103`