Calculating pH of 0.1 M NaHCO3 with Ka values | Salt Hydrolysis Formula

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SUMMARY

The pH of a 0.1 M NaHCO3 solution is calculated using the salt hydrolysis formula, considering the dissociation constants Ka1 and Ka2 for carbonic acid (H2CO3). The values provided are Ka1 = 4.3 * 10-7 and Ka2 = 5.61 * 10-11. The calculation involves determining K_h using the formula K_h = Kw/Ka1, resulting in K_h = 2.3 * 10-8, which is greater than Ka2. However, neglecting dissociation leads to an incorrect pH value, highlighting the importance of considering the amphiprotic nature of the salt.

PREREQUISITES
  • Understanding of acid-base chemistry and pH calculations
  • Familiarity with the concepts of dissociation constants (Ka values)
  • Knowledge of the salt hydrolysis formula
  • Basic grasp of amphiprotic substances
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  • Learn about the properties of amphiprotic salts
  • Explore the calculation of pH for weak acids and their salts
  • Investigate the relationship between Ka values and pH in buffer solutions
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Homework Statement



Find pH of [tex]0.1M NaHCO_3[/tex]

[tex]Ka_1 (H_2CO_3) = 4.3 * 10^{ - 7} , Ka_2 (H_2CO_3) = 5.61 * 10^{ - 11}[/tex]

Homework Equations



[tex]pH = \frac {1}{2}(14 + pKa_1 + logC)[/tex]

The Attempt at a Solution



Now [tex]K_h = \frac {Kw}{Ka_1} = 2.3 * 10^{ - 8} > > Ka2[/tex]

So I neglect dissociation and use salt hydrolysis formula.

But this gives wrong answer.
 
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