Question

Predict which of the following metals reacts with aqueous cadmium(II) nitrate. (a) \(\mathrm{Hg}\) (b) \(\mathbf{P b}\) (c) Ni (d) \(\mathrm{Cr}\)

Short answer

Chromium (Cr) is the metal that reacts with aqueous cadmium(II) nitrate.

Step-by-step solution

Understand the Reactivity Series

The first step is to recognize that metal reactivity is determined by its placement in the reactivity series. Metals higher in the series can displace those lower when reacted with their compounds in solution. Study the reactivity series of metals to identify which metals can displace cadmium.

Locate Cadmium and Compare

Cadmium (48;Cd49;) is located below iron and above hydrogen in the reactivity series. To determine which metals will react with cadmium(II) nitrate, compare the positions of mercury (48;Hg49;), lead (48;Pb49;), nickel (48;Ni49;), and chromium (48;Cr49;) in the reactivity series.

Evaluate Metal Reactivity

Examine each metal's placement: - Mercury (48;Hg49;) is less reactive than cadmium, as it is lower in the series. - Lead (48;Pb49;) is also generally less reactive. - Nickel (48;Ni49;) is slightly more reactive, being just above cadmium. - Chromium (48;Cr49;) is much more reactive and higher up in the series.

Predict the Reaction

Based on the reactivity comparisons, chromium (48;Cr49;) is likely to react with cadmium(II) nitrate due to its higher reactivity. Nickel (48;Ni49;) is on the borderline but typically can also displace cadmium under the right conditions.

Key concepts

Metal Reactivity

Metal reactivity is a crucial concept when predicting how different metals behave during chemical reactions, especially in solutions. Each metal has a specific placement within the reactivity series, which organizes metals according to their ability to displace other metals from compounds. This predominantly depends on the metal’s tendency to lose electrons and form positive ions.

The general rule is that metals at the higher end of the series are more reactive and, therefore, can displace metals situated lower down. For instance, potassium and sodium are towards the top, indicating high reactivity, while metals like gold and platinum are far less reactive. Understanding this sequence allows us to predict potential reactions involving metals and compounds in aqueous solutions.

Displacement Reactions

Displacement reactions are specific types of redox reactions where a more reactive metal displaces a less reactive metal from a compound or solution. This occurs because the more reactive metal will readily donate electrons (undergo oxidation) and form ions, pushing the less reactive metal out of the compound.

Consider the example of a solution of cadmium(II) nitrate: when presented with a metal higher on the reactivity series, a reaction can occur resulting in the free form of cadmium and a new compound with the displacing metal. The reactivity series acts as a handy guide; it predicts if and how these metals will interact based on their relative positions.

Cadmium(II) Nitrate

Cadmium(II) nitrate, represented as Cd(NO\(_3\))\(_2\), is a soluble salt commonly found in solutions during displacement reactions. It contains cadmium ions ( ext{Cd}^{2+}) and nitrate ions ( ext{NO}_3^-), playing a significant role in determining interaction potential with other metals.

To understand if a reaction will occur, compare the reactivities of cadmium to other metals in question. If the metal tested is higher in the reactivity series, it can displace cadmium from the nitrate solution, resulting in cadmium's precipitation and the formation of a new compound. In our examined case, chromium and nickel both hold the potential to react with cadmium(II) nitrate, with chromium being the most likely due to its position much higher in the series.