1. What volume of \( 0.40 \mathrm{MBa}(\mathrm{OH})_{2} \) must be added to \( 50 \mathrm{~mL} \) of \( 0.30 \mathrm{MNaOH} \) to give a solution \( 0.50 \mathrm{M} \) in \( \mathrm{OH}^{-} \)?
2. For a solution of \( \mathrm{Pb}^{2+} \);
a. Calculate the molar concentrations of \( 1 \mathrm{mg} / \mathrm{L}(1.00 \mathrm{ppm}) \) solution of \( \mathrm{Pb}^{2+} \)
b. What weight of \( \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2} \) will have to be dissolved in 1 liter of water to prepare a 100 \( \mathrm{mg} / \mathrm{L}(100 \mathrm{ppm}) \mathrm{Pb}^{2+} \) solution?
3. What weight of pyrite ore (impure \( \mathrm{FeS}_{2} \) ) must be taken for analysis so that the \( \mathrm{BaSO}_{4} \) precipitate weight obtained will be equal to one-half that of the percent \( \mathrm{S} \) in the sample?
\( [5] \)
4. A buffer solution is prepared by adding \( 20 \mathrm{~mL} \) of \( 0.10 \mathrm{M} \) sodium hydroxide solution to \( 50 \mathrm{~mL} \) o \( 0.10 \mathrm{M} \) acetic acid solution. What is the \( \mathrm{pH} \) of the buffer?
[5]
