Problem 8 - Chemistry: The Central Science

Question

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]

Step-by-Step Solution

Answer

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 1: 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.

Step 2: 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.

Step 3: 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.

Step 4: 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.