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Chapter 4: Problem 8

The labels have fallen off three bottles containing powdered samples of metals; one contains zinc, one lead, and the other platinum. You have three solutions at your disposal: \(1 \mathrm{M}\) sodium nitrate, \(1 \mathrm{M}\) nitric acid, and \(1 \mathrm{M}\) nickel nitrate. How could you use these solutions to determine the identities of each metal powder? [Section 4.4]

Short Answer

Expert verified
To identify the metal powders, perform the following tests: 1. Add \(1M NaNO_3\) to each powder: No reaction will occur with zinc, lead, or platinum. 2. Add \(1M HNO_3\) to each powder: Zinc and lead will react, but platinum will not. The powder that does not react is platinum. 3. Add \(1M Ni(NO_3)_2\) to the remaining powders: Zinc will react, displacing nickel, but lead will not. The powder that reacts is zinc, and the one that does not is lead. Thus, the identities of the powders are determined: platinum does not react with any solution; zinc reacts with nitric acid and nickel nitrate; and lead reacts only with nitric acid.

Step by step solution

01

Add Sodium Nitrate solution to each metal powder

After adding the sodium nitrate solution to each metal powder, observe for any reactions. However, as none of the metals being zinc, lead, and platinum are reactive enough to react with sodium nitrate, no reaction shall be observed.
02

Add Nitric Acid solution to each metal powder

After adding the nitric acid solution to each metal powder, observe the reactions. Both zinc and lead will react with the nitric acid to release hydrogen gas and form the corresponding nitrates. However, platinum will not react with nitric acid. Thus, the sample which does not react is the platinum powder.
03

Add Nickel Nitrate solution to the remaining two metal powders

After adding the nickel nitrate solution, observe the reactions. According to the reactivity series, zinc is more reactive than nickel and will displace nickel from its nitrate solution. Lead, however, will not react with nickel nitrate. Thus, the metal sample which reacts with nickel nitrate is zinc, and the one which does not react is lead.
04

Conclusion

The metal which does not react with either of the three solutions: sodium nitrate, nitric acid, and nickel nitrate is Platinum. The metal which reacts with nitric acid and nickel nitrate is Zinc. The metal that only reacts with nitric acid but not with nickel nitrate is Lead. So, through these reactions using the three different solutions, the identity of the three metal powders can be determined.

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Most popular questions from this chapter

Suppose you have a solution that might contain any or all of the following cations: \(\mathrm{Ni}^{2+}, \mathrm{Ag}^{+}, \mathrm{Sr}^{2+}\), and \(\mathrm{Mn}^{2+}\). Addition of \(\mathrm{HCl}\) solution causes a precipitate to form. After filtering off the precipitate, \(\mathrm{H}_{2} \mathrm{SO}_{4}\) solution is added to the resulting solution and another precipitate forms. This is filtered off, and a solution of \(\mathrm{NaOH}\) is added to the resulting solution. No precipitate is observed. Which ions are present in each of the precipitates? Which of the four ions listed above must be absent from the original solution?

(a) Calculate the molarity of a solution made by dissolving \(12.5\) grams of \(\mathrm{Na}_{2} \mathrm{CrO}_{4}\) in enough water to form exactly \(750 \mathrm{~mL}\) of solution. (b) How many moles of \(\mathrm{KBr}\) are present in \(150 \mathrm{~mL}\) of a \(0.112 \mathrm{M}\) solution? (c) How many milliliters of \(6.1 \mathrm{M} \mathrm{HCl}\) solution are needed to obtain \(0.150 \mathrm{~mol}\) of \(\mathrm{HCl}\) ?

We have seen that ions in aqueous solution are stabilized by the attractions between the ions and the water molecules. Why then do some pairs of ions in solution form precipitates? [Section 4.2]

The following reactions (note that the arrows are pointing only one direction) can be used to prepare an activity series for the halogens: $$ \begin{gathered} \mathrm{Br}_{2}(a q)+2 \mathrm{NaI}(a q) \longrightarrow 2 \mathrm{NaBr}(a q)+\mathrm{I}_{2}(a q) \\ \mathrm{Cl}_{2}(a q)+2 \mathrm{NaBr}(a q) \longrightarrow 2 \mathrm{NaCl}(a q)+\mathrm{Br}_{2}(a q) \end{gathered} $$ (a) Which elemental halogen would you predict is the most stable, upon mixing with other halides? (b) Predict whether a reaction will occur when elemental chlorine and potassium iodide are mixed. (c) Predict whether a reaction will occur when elemental bromine and lithium chloride are mixed.

(a) You have a stock solution of \(14.8 \mathrm{M} \mathrm{NH}_{3}\). How many milliliters of this solution should you dilute to make \(1000.0 \mathrm{~mL}\) of \(0.250 \mathrm{M} \mathrm{NH}_{3}\) ? (b) If you take a \(10.0\)-mL portion of the stock solution and dilute it to a total volume of \(0.500 \mathrm{~L}\), what will be the concentration of the final solution?
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