Question

What volume of 0.826 MKOH solution do you need to make 3.74 L of a solution with a pH of 12.500?

Answer 1

Given that –

• pH = 12.5

We know that –

• pH + pOH = 14

Then –

`\qquad`
`\bf\longrightarrow pOH = 14 -12.5`

`\qquad`
`\sf \longrightarrow pOH = 1.5`

`\qquad`
`\sf \longrightarrow [OH^- ] = 10^(-1.5 )`

`\qquad`
`\bf \longrightarrow [OH^-] = 3.16 × 10^(-2)`

Now the number of moles of KOH need to ensure that concentration of Hydroxide anions is equal to –

`\qquad`
`\bf \longrightarrow 3.74\: L * (3.16× 10^(-2))/(1 \: L )`

`\qquad`
`\bf \longrightarrow 1. 18 × 10^(-1 )M`

Volume of the solution contains the need number of moles of Hydroxide anions –

`\qquad`
`\sf \longrightarrow ( 1.18×10^(-1) \: moles \: OH^-)/(0.826 \: moles \: OH^-)`

`\qquad`
`\sf \longrightarrow 0.143 L`

`\qquad`
`\sf \longrightarrow 0.143 * 1000`

`\qquad`
`\pink{\bf\longrightarrow 143 mL }`

______________________________________