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Chapter 24: Problem 25

Write equations to represent the following observations. (a) A mixture of \(\hat{M g}(O H)_{2}(s)\) and \(Z n(O H)_{2}(s)\) is treated with \(\mathrm{NH}_{3}(\mathrm{aq}) .\) The \(\mathrm{Zn}(\mathrm{OH})_{2}\) dissolves, but the \(\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s})\) is left behind. (b) When \(\mathrm{NaOH}(\mathrm{aq})\) is added to \(\mathrm{CuSO}_{4}(\mathrm{aq}),\) a pale blue precipitate forms. If \(\mathrm{NH}_{3}(\) aq) is added, the precipitate redissolves, producing a solution with an intense deep blue color. If this deep blue solution is made acidic with \(\mathrm{HNO}_{3}(\mathrm{aq}),\) the color is converted back to pale blue.

Short Answer

Expert verified
The chemical reactions for the observations are: (a) \( Zn(OH)2(s) + 4NH3(aq) \rightarrow [Zn(NH3)4]^{2+}(aq) + 2OH^{-}(aq) \) and \(Mg(OH)2(s)\); (b) \(CuSO4(aq) + 2NaOH(aq) \rightarrow Cu(OH)2(s) \downarrow + Na2SO4(aq)\), \(Cu(OH)2(s) + 4NH3(aq) \rightarrow [Cu(NH3)4]^{2+}(aq) + 2OH^{-}(aq)\), and \([Cu(NH3)4]^{2+}(aq) + 6HNO3(aq) \rightarrow Cu(NO3)2(aq) + 4NO3^{-}(aq) + 6H2O(l) + 2NO2(g) \uparrow \)

Step by step solution

01

Writing Equation for Observation (a)

There are two parts here. One is Zn(OH)2 dissolving in NH3(aq) and the other is Mg(OH)2 not dissolving. The reaction of Zn(OH)2 with NH3(aq) can be written as:\[ Zn(OH)2(s) + 4NH3(aq) \rightarrow [Zn(NH3)4]^{2+}(aq) + 2OH^{-}(aq) \]The undissolved Mg(OH)2 is just expressed as:\[ Mg(OH)2(s) \] No reaction takes place with Mg(OH)2, so it remains in its original form.
02

Writing Equation for Observation (b)

Similar to step 1, there are also multiple parts here. First, NaOH(aq) reacts with CuSO4(aq) to form a pale blue precipitate:\[ CuSO4(aq) + 2NaOH(aq) \rightarrow Cu(OH)2(s) \downarrow + Na2SO4(aq) \]Next, the formed Cu(OH)2 reacts with NH3(aq) and dissolves, forming a deep blue solution:\[ Cu(OH)2(s) + 4NH3(aq) \rightarrow [Cu(NH3)4]^{2+}(aq) + 2OH^{-}(aq) \]Finally, adding HNO3(aq) to the deep blue solution acidifies the solution and returns it back to pale blue color:\[ [Cu(NH3)4]^{2+}(aq) + 6HNO3(aq) \rightarrow Cu(NO3)2(aq) + 4NO3^{-}(aq) + 6H2O(l) + 2NO2(g) \uparrow \]

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Most popular questions from this chapter

Write a series of equations to show the stepwise displacement of \(\mathrm{H}_{2} \mathrm{O}\) ligands in \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) by ethylenediamine, for which \(\log K_{1}=4.34, \log K_{2}=3.31\), and \(\log K_{3}=2.05 .\) What is the overall formation constant, \(\beta_{3}=K_{f},\) for \(\left[\mathrm{Fe}(\mathrm{en})_{3}\right]^{3+} ?\)

The compound \(\mathrm{CoCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O} \cdot 4 \mathrm{NH}_{3}\) may be one of the hydrate isomers \(\left[\mathrm{CoCl}\left(\mathrm{H}_{2} \mathrm{O}\right)\left(\mathrm{NH}_{3}\right)_{4}\right] \mathrm{Cl} \cdot \mathrm{H}_{2} \mathrm{O}\) or \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\left(\mathrm{NH}_{3}\right)_{4}\right] \mathrm{Cl}_{2} .\) A \(0.10 \mathrm{M}\) aqueous solution of the compound is found to have a freezing point of \(-0.56^{\circ} \mathrm{C} .\) Determine the correct formula of the compound. The freezing-point depression constant for water is \(1.86 \mathrm{mol}\) \(\mathrm{kg}^{-1}\) \(^{\circ} \mathrm{C}\), and for aqueous solutions, molarity and molality can be taken as approximately equal.

Of the following complex ions, the one that exhibits isomerism is (a) \(\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right]^{+} ;\) (b) \(\left[\mathrm{CoNO}_{2}\left(\mathrm{NH}_{3}\right)_{5}\right]^{2+};\) \((\mathrm{c}) \quad\left[\mathrm{Pt}(\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2}\right]^{2+};\) (d) \(\quad\left[\mathrm{CoCl}\left(\mathrm{NH}_{3}\right)_{5}\right]^{2+};\) (e) \(\left[\mathrm{PtCl}_{6}\right]^{2-}\).

If \(\mathrm{A}, \mathrm{B}, \mathrm{C},\) and \(\mathrm{D}\) are four different ligands, (a) how many geometric isomers will be found for square-planar \([\mathrm{PtABCD}]^{2+} ?\) (b) Will tetrahedral \([\mathrm{ZnABCD}]^{2+}\) display optical isomerism?

How many isomers are there of the complex ion \(\left[\mathrm{CoCl}_{2}(\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2}\right]^{+} ?\) Sketch their structures.
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