Chapter 25

The \(\mathrm{pH}\) of a \(0.010 \mathrm{M}\) HOBr solution is 5.3 a. What is \(\left[\mathrm{H}^{+}\right]\) in that solution? ____M b. What is \(\left[\mathrm{OBr}^{-}\right] ?\) What is [HOBr]? (Where do the \(\mathrm{H}^{+}\) and \(\mathrm{OBr}^{-}\) ions come from?) $$\mathbf{M}: \quad \mathbf{M}$$ c. What is the value of \(K_{a}\) for HOBr? What is the value of \(p K_{a} ?\)

Formic acid, HFor, has a \(K_{a}\) value of \(1.8 \times 10^{-4}\). A student is asked to prepare a buffer having a pH of 3.85 from a solution of formic acid and a solution of sodium formate having the same molarity. How many milliliters of the NaFor solution should she add to \(20.0 \mathrm{mL}\) of the HFor solution to make the buffer? (See discussion of buffers.) _____mL