**QUESTION**

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2-40. Exactly $750.0 \mathrm{~mL}$ of a solution that contains $500.0 \mathrm{ppm}$ of $\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}$ is mixed with $200.0 \mathrm{~mL}$ of a solution that was $0.04100 \mathrm{M}$ in $\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}$. (a) What mass of solid $\mathrm{BaSO}_{4}$ is formed? (b) What is the molar concentration of the unreacted reagent $\left[\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}\right.$ or $\left.\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}\right]$ ?

2-18. Calculate the molar $\mathrm{H}_{3} \mathrm{O}^{+}$ion concentration of a solution that has a $\mathrm{pH}$ of (a) 3.73 . (b) 3.28 . (c) 0.59 . (d) 11.29 . (e) 7.62 . (f) 5.19 . (g) -0.76 . (h) -0.42 .