Question

Find the pH of a 0.140 M solution of a weak monoprotic acid having Ka= 1.0×10⁻³.

Express your answer to two decimal places.

pH =

1.95

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Correct

Significant Figures Feedback: Your answer 1.93 was either rounded differently or used a different number of significant figures than required for this part.

Part D

Find the percent dissociation of this solution.

Express your answer using two significant figures.

%

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Not quite. Check through your calculations; you may have made a rounding error or used the wrong number of significant figures.

Part E

Find the pH of a 0.140 M solution of a weak monoprotic acid having Ka= 0.18.

Express your answer to two decimal places.

pH =

.79

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Part F

Find the percent dissociation of this solution.

Express your answer using two significant figures.

I keep getting the answer wrong due to sig figs and its really pissing me off because i know how to do this but keep gettting wrong number. MASTERCHEMISTRY

Answer 1

part D

Ka = cx^2

C = concentration of acid = 0.14 M

x = degree of dissociation = ?

1*10^-3 = 0.14*x^2

x = 0.0845

percentage dissociation = x*100

           = 0.0845*100 = 8.45%

part E

pH of weakacid = 1/2(pka-logC)

    pka = -logka = -log0.18 = 0.745

                = 1/2(0.745-log0.14)

                = 0.8

in this part please check Ka = 0.18 is correct or not