Twenty-five mL of 0.150 M hydrofluoric acid, HF, is titrated with 0.100 M potass

ID: 799891 • Letter: T

Question

Twenty-five mL of 0.150 M hydrofluoric acid, HF, is titrated with 0.100 M potassium hydroxide.

What is the pH of the acid initially (before any base is added)?

What volume of potassium hydroxide must be added to reach the equivalence point?

What is the pH of the solution at the halfway point of the titration (halfway to the equivalence

point)?

What is the pH of the solution at the equivalence point?

Plot the titration curve. Make sure you have enough data points to draw your curve.

What indicator would you choose for this titration? What color change would you observe with the chosen indicator? Explain your choice.

Ka of HF=7.2*10^-4

let eh dissociation be x.so,

7.2*10^-4=x^2/(0.15-x)

or x=0.01

so, pH=-log(0.01)

2)let the volume of bas eadded be v.so,

equating the number of moles,

0.15*25=0.1*v

or v=37.5 mL

3)pH=pKa+log(salt/acid)

=3.14

4)concentration of the salt formed=25*0.15/(25+37.5)

=0.06 M

the salt formed will be a salt of strong base and a weak acid.

so,

pH=7+0.5*pKa+0.5log(C)

=7+0.5*3.14+0.5*log(0.06)

=7.96

6)i would chooseNaphtholphthalein. color range=reddish to blish

i would choose it since the reaction equvalence occurs at close to the pH of 7

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.