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Methanoic acid has a Ka=1.6X10-4. Calculate the pH of the final solution when 23.90 mL of...

Methanoic acid has a Ka=1.6X10-4. Calculate the pH of the final solution when 23.90 mL of 0.100M NaOH is added to 25.00 mL of 0.100 M methanoic acid

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Expert Solution

Ka = 1.6 x10^-4

NaOH = 23.90 ml of 0.100M

number of moles of NaOH = 0.100M x 0.02390L = 0.00239 moles

Methanoic acid = 25.00ml of 0.100M

number of moles of Methanoic acid = 0.100M x 0.02500L = 0.0025 moles

Ka = 1.6 x 10^-4

-log(Ka) = -log(1.6 x10^-4)

Pka = 3.79

Methanoic acid = HCOOH

                   HCOOH     +    NaOH ---------------------   HCOONa      + H2O

Initial            0.0025           0.00239                                   0

change    - 0.00239        - 0.00239                              + 0.00239

equilibrium               0.00011                0                                   + 0.00239

PH = Pka + log[salt]/[acid]

PH = 3.79 + log(0.00239/0.00011)

PH = 5.13

PH of the solution = 5.13


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