- #1

TrueStar

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## Homework Statement

In our chemistry lab, we estimated the pH values of various solutions using six different indicators. Based on these estimated pH values, we must calculate [H+] and the estimated Ka or Kb values.

## Homework Equations

For pH - ph=-log[H+}

For Ka and Kb values - Concentrations of Product / Concentrations of Reactant

## The Attempt at a Solution

I think I'm having the most trouble with the salts, like NaCl and ZnCl2. My estimated pH values for NaCl and ZnCl2 are 6.7 and 4.3 respectively.

I think I'm supposed to set up an ICE table for problems likes these, but I'm not sure. With another solution we tried (NaCH3CO2), you clearly see that OH- is produced when added into water. In this case, we took out estimated pH (7.7) and subtracted that number from 14 to get 6.3 which is the pOH. From this, I calculated that the concentration of OH is about 5.01x10^-7. I divided the concentration of NaCH3CO2, which was 0.10, by this number and I think my estimated Kb value is about 5x10^-6.

I don't know how to translate these kinds of calculations to the salts. NaCl is neutral.

I do know that water goes through autoionization, but I'm not sure if this has any role in calculating the Ka/Kb values for NaCl and ZnCl2.

Long story short, I'm not sure how to calculate my estimated Ka/Kb values for NaCl and ZnCl2...even assuming I'm calculating them correctly for solutions like NaCH3CO2.

Thank you!