c) Calculate the pH of an aqueous solution obtained by mixing 50 ml of 0.2 M `HCI` with `50 ml 0.1 M" " NaOH.`

Explanation

No. of moles of HCI `=0.2 xx50xx10^(-3)`
`=10xx10^(-3)`
No. of moles of NaOH `=0.1 xx50xx10^(-3)`
`=5xx10^(-3)`
No. of moles of HCI after mixing
`=10xx10^(-3)-5xx10^(-3)`
`5xx10^(-3)`
after mixing total volume `= 100` mL
`therefore` Concentration of HCI in moles per litre
`=(5xx10^(-3)"Mole")/(100xx10^(-3) L)`
`[H_3 O^+]=5xx10^(-2) M`
`pH=-log (5xx10^(-2))`
`=2-log5`
`=2-0.6990`
`=1.30`.