#7 & #8 7. 40 ml of .1M NaOH added to sol\'n of 6 mmoles of Carbonic acid. pH=?

Question

#7 & #8 7. 40 ml of .1M NaOH added to sol'n of 6 mmoles of Carbonic acid. pH=? e millimoles (mmoles) the number calculate the number of l e J 5 n holes e. Calculate the pH of a solution which contains 5 mmoles carbonic acid and 5 moles. sodium bicarbonate e 3 Calculate the number of mmoles of carbonic acid and sodium bicarbonate after the addition of 0.6 mmoles HCl to the solution above. 5 10 -0. g. Calculate the pH after the addition of the HC1 in S. 7. Forty ml of 0.1 M NaOH have been added to a solution of 6 mm es of carbonic acid. Calculate the pH ymles NA 8. Calculate the pH if80 ml of 0.1 M NaOH are added to a solution of 6 mmoes of carbonic acid. a. Write the ionization reactions for phosphoric acid and indicate which pKa goes with each ionization. Given 80 mmoles phosphoric acid, calculate the pH after the addition of 5 mmoles NaoH. Given 80 mmoles phosphoric acid, calculate the pH after the addition of 50 mmoles NaOH. Given 80 mmoles phosphoric acid, calculate the pH after the addition of 110 mmoles TaOH.

Explanation / Answer

Q7.

mol = MV = 40*0.1 = 4 mmol ofNaOH

mol = 6mmol of H2CO3

so

reaction --> 4 mmol of H2CO3 reac tto form HCO3- moles

moles of acid left = 6-4 = 2 mmol of H2CO3 left

so

this is a buffer

pH = pKa 1+ log(HCO3- / H2CO3)

pH = 6.36 + log(4/2) = 6.661

Q8

pH for mix if:

mmol = MV = 80*0.1 = 8 mmol of base

mmol of acid = 6

there is

6 mol of base reating with 6 mol of diprotic acid, all H2CO3 is reacted..

then HCO3- is left...

6 mol of HCO3- are formed, then 2 mol of OH- are left

6-2 = 4 mmol of HCO3- are left

2 mmol of CO3-2 are formed

so

pH = pKa2 + log(CO3-2/HCO3-)

pH = 10.32 + log(2/4) = 10.0189

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