A 20.0 mL of 0.27 M solution of the salt NaA has a pH of 8.70. a) Calculate the pk, value of the acid HA.

(Correct to 3 sig. fig)

b) Calculate the pH of a solution containing 0.3 M HA and 0.1 M NaA.

(Correct to 3 sig. fig)

Thanks!!

a) 3.969

b) 3.487

Explanation:

Given data:

m =  0.27 M

pH = 8.7

a) Calculate PKa of acid HA

pH value = 1/2 ( Pkw + Pka + log C )

    8.7 * 2 = 14 + log C + Pka

        17.4 = 14 + log ( 0.27 ) + Pka

∴Pka = 17.4 - 14.5686 = 3.9686 ≈ 3.969

b) Calculate the pH of solution

pH = pKa + log ( salt / acid )

     = 3.9686 + log ( 0.1 / 0.3 )

     = 3.487

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a