Problem 85
Describe a simple test that would allow you to distinguish between \(\mathrm{AgNO}_{3}(s)\) and \(\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(s)\)
Problem 86
The \(\mathrm{p} K_{\mathrm{a}}\) of the indicator methyl orange is \(3.46 .\) Over what \(\mathrm{pH}\) range does this indicator change from 90 percent HIn to 90 percent \(\mathrm{In}^{-}\) ?
Problem 87
The \(\mathrm{p} K_{\mathrm{a}}\) of the indicator methyl orange is \(3.46 .\) Over what \(\mathrm{pH}\) range does this indicator change from 90 Dercent HIn to 90 percent In \(^{-}\) ?
Problem 88
Sketch the titration curve of a weak acid with a strong base like the one shown in Figure 17.4 . On your graph, indicate the volume of base used at the equivalence point and also at the half-equivalence point, that is, the point at which half of the acid has been neutralized. Explain how the measured \(\mathrm{pH}\) at the half-equivalence point can be used to determine \(K_{\mathrm{a}}\) of the acid.
Problem 89
A \(200-\mathrm{mL}\) volume of \(\mathrm{NaOH}\) solution was added to \(400 \mathrm{~mL}\) of a \(2.00 \mathrm{M} \mathrm{HNO}_{2}\) solution. The \(\mathrm{pH}\) of the mixed solution was 1.50 units greater than that of the original acid solution. Calculate the molarity of the \(\mathrm{NaOH}\) solution.
Problem 90
The \(\mathrm{p} K_{\mathrm{a}}\) of butyric acid (HBut) is 4.7. Calculate \(K_{\mathrm{b}}\) for the butyrate ion (But \(^{-}\) ).
Problem 92
\(\mathrm{Cd}(\mathrm{OH})_{2}\) is an insoluble compound. It dissolves in excess \(\mathrm{NaOH}\) in solution. Write a balanced ionic equation for this reaction. What type of reaction is this?
Problem 94
A student mixes \(50.0 \mathrm{~mL}\) of \(1.00 \mathrm{M} \mathrm{Ba}(\mathrm{OH})_{2}\) with \(86.4 \mathrm{~mL}\) of \(0.494 \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4} .\) Calculate the mass of \(\mathrm{BaSO}_{4}\) formed and the \(\mathrm{pH}\) of the mixed solution.
Problem 95
For which of the following reactions is the equilibrium constant called a solubility product? (a) \(\mathrm{Zn}(\mathrm{OH})_{2}(s)+2 \mathrm{OH}^{-}(a q) \rightleftarrows \mathrm{Zn}(\mathrm{OH})_{4}^{2-}(a q)\) (b) \(3 \mathrm{Ca}^{2+}(a q)+2 \mathrm{PO}_{4}^{3-}(a q) \rightleftharpoons \mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}(s)\) (c) \(\mathrm{CaCO}_{3}(s)+2 \mathrm{H}^{+}(a q) \rightleftharpoons\) \(\mathrm{Ca}^{2+}(a q)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{CO}_{2}(g)\) (d) \(\mathrm{PbI}_{2}(s) \rightleftharpoons \mathrm{Pb}^{2+}(a q)+2 \mathrm{I}^{-}(a q)\)
Problem 96
Water containing \(\mathrm{Ca}^{2+}\) and \(\mathrm{Mg}^{2+}\) ions is called hard water and is unsuitable for some household and industrial use because these ions react with soap to form insoluble salts, or curds. One way to remove the \(\mathrm{Ca}^{2+}\) ions from hard water is by adding washing soda \(\left(\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O}\right)\). (a) The molar solubility of \(\mathrm{CaCO}_{3}\) is \(9.3 \times 10^{-5} \mathrm{M}\). What is its molar solubility in a \(0.050 \mathrm{M} \mathrm{Na}_{2} \mathrm{CO}_{3}\) solution? (b) Why are \(\mathrm{Mg}^{2+}\) ions not removed by this procedure? (c) The \(\mathrm{Mg}^{2+}\) ions are removed as \(\mathrm{Mg}(\mathrm{OH})_{2}\) by adding slaked lime \(\left[\mathrm{Ca}(\mathrm{OH})_{2}\right]\) to the water to produce a saturated solution. Calculate the \(\mathrm{pH}\) of a saturated \(\mathrm{Ca}(\mathrm{OH})_{2}\) solution. (d) What is the concentration of \(\mathrm{Mg}^{2+}\) ions at this \(\mathrm{pH}\) ? (e) In general, which ion \(\left(\mathrm{Ca}^{2+}\right.\) or \(\mathrm{Mg}^{2+}\) ) would you remove first? Why?
