The Ka's for H2CO3 are K1 = 4.5 x 10^-11. Calculate the pH of the solution...

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The Ka's for H2CO3 are K1 = 4.5 x 10^-11. Calculatethe pH of the solution when 45.9 ml of 0.25 M KHCO3 is mixed witha)35 mL 0.15 M HBr.Â Â Â Â b) 50.0 mL of 0.15 MKOH

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4.1 Ratings (658 Votes)

H2CO3 Ka1 = 4.3 x 10^-7

Ka2 = 5.6 x 10^-11

millimoles of HCO3- = 45.9 x 0.25 = 11.475

millimoles of HBr = 35 x 0.15 = 5.25

HCO3- +Â Â Â Â Â Â H+Â Â ----------------> H2CO3

11.475Â Â Â Â Â 5.25Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0

6.225 Â Â Â Â Â Â Â Â Â Â 0 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 5.25

pOH = pKb1 + log [HCO3- / H2CO3]

Â Â Â Â Â Â Â = 7.63 + log [6.225 / 5.25]

Â Â Â Â Â Â Â = 7.70

pH = 14 - 7.70 = 6.3

pH = 6.30

(b)

millimoles of KOH = 50 x 0.15 = 7.5

HCO3- +Â Â OH-Â Â -------------------> CO32- + H2O

11.475Â Â Â Â Â Â 7.5Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0Â Â Â Â Â Â Â Â Â Â Â 0

3.975Â Â Â Â Â Â Â Â Â Â 0Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 7.5Â Â Â Â Â Â Â Â Â 7.5

pH = pKa2 + log [CO32- / HCO3-]

Â Â Â Â = 10.25 + log [7.5 / 3.975]

Â Â Â Â = 10.53

pH = 10.53

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The Ka's for H2CO3 are K1 = 4.5 x 10^-11. Calculate the pH of the solution...

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70.2K

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Question

Chemistry

The Ka's for H2CO3 are K1 = 4.5 x 10^-11. Calculatethe pH of the solution when 45.9 ml of 0.25 M KHCO3 is mixed witha)35 mL 0.15 M HBr.Â Â Â Â b) 50.0 mL of 0.15 MKOH

Answer & Explanation Solved by verified expert

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