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## Homework Statement

1. a) Calculate pH of solution that results form mixing 16.5 mL of 0.182 M HCN (aq) with 29.2 mL of 0.105 M NaCN. Ka of HCN is 4.9*10^-10

b) and how could we determine what 'indicator' would be the 'best' to use for a titration between 0.10 M CH3NH2 with 0.10 M HBr?

## Homework Equations

pH = Pka + log([A-]/[HA])

ka=kw/kb

## The Attempt at a Solution

a) pH = -log(4.9*10^-10) + log(.105/.182), which turns out wrong, the answer is actually 9.32(why?).

b) found the kb of CH3NH2 to be 4.4*10^-4, thus ka is found from the given equation. anyway it gives something in the range of 10 or so, the answer is actually 4-6, why? These questions have no likes in the textbook that my professor issued and the material is confusing. Please help.