Question

The metal cadmium tends to form ${\mathrm{Cd}}^{2+}$ ions. The following observations are made: (i) When a strip of zinc metal is placed in ${\mathrm{CdCl}}_2(aq)$, cadmium metal is deposited on the strip. (ii) When a strip of cadmium metal is placed in $\mathrm{Ni}{\left({\mathrm{NO}}_3\right)}_2(aq)$, nickel metal is deposited on the strip. (a) Write net ionic equations to explain each of the observations made above. (b) What can you conclude about the position of cadmium in the activity series? (c) What experiments would you need to perform to locate more precisely the position of cadmium in the activity series?

Short answer

(a) The net ionic equations for the described observations are: (i) Zn(s) + Cd^2+(aq) -> Zn^2+(aq) + Cd(s) (ii) Cd(s) + Ni^2+(aq) -> Cd^2+(aq) + Ni(s) (b) Based on these reactions, cadmium's position in the activity series lies between zinc and nickel. (c) To determine cadmium's position more precisely, perform experiments with other metals and their salts. Observe the displacement reactions by placing cadmium in various metal salt solutions or placing other metals in a cadmium salt solution.

Step-by-step solution

Write the reaction when zinc is placed in CdCl2(aq)

When a strip of zinc metal is placed in CdCl2(aq), cadmium metal is deposited on the strip. This implies that zinc metal displaces cadmium ions in the solution. The reaction can be written as: Zn(s) + CdCl2(aq) -> ZnCl2(aq) + Cd(s)

Write the net ionic equation for Observation (i)

To write the net ionic equation, we need to separate the aqueous compounds into their individual ions. The net ionic equation is obtained by removing the spectator ions (the ions that do not participate in the reaction) from the total ionic equation. The spectator ions in this reaction are Cl⁻ ions: Zn(s) + Cd^2+(aq) -> Zn^2+(aq) + Cd(s)

Write the reaction when cadmium is placed in Ni(NO3)2(aq)

When a strip of cadmium metal is placed in Ni(NO3)2(aq), nickel metal is deposited on the strip. This means that the cadmium metal displaces nickel ions in the solution. The reaction can be written as: Cd(s) + Ni(NO3)2(aq) -> Cd(NO3)2(aq) + Ni(s)

Write the net ionic equation for Observation (ii)

We will separate the aqueous compounds into their individual ions and then remove the spectator ions (NO3⁻ ions in this case) from the total ionic equation: Cd(s) + Ni^2+(aq) -> Cd^2+(aq) + Ni(s)

Determine the position of cadmium in the activity series based on the observations

In the activity series of metals, metals higher in the series can displace metals that are lower in the series from their aqueous solutions. From the given observations, we can conclude that: 1. Zinc is more active than cadmium, as it can displace Cd^2+ ions in the solution. 2. Cadmium is more active than nickel, as it can displace Ni^2+ ions in the solution. Thus, the position of cadmium in the activity series is between zinc and nickel.

Discuss the experiments needed to locate the position of cadmium more precisely in the activity series

To locate the position of cadmium more precisely in the activity series, we can perform experiments similar to the given observations, but this time with other metals to evaluate their reactivity compared to cadmium. Some possible experiments include: 1. Placing a strip of cadmium in the aqueous solutions of other metal salts (e.g., CuSO4, MgCl2, Fe(NO3)3) and observing any displacement reactions. 2. Placing strips of other metals in a solution of cadmium salt (e.g., Cd(NO3)2) and observing any displacement reactions. Observing the outcomes of these experiments would provide more information about the relative activity of cadmium compared to other metals, helping us locate its position more precisely in the activity series.