Which pairs of reactants will result in a chemical reaction? Refer to the activity series as needed. Ni(s) + MgCl2(aq) Pb(s) + Cu(NO2)(aq) Mn(s) + AgClO2(aq) Pt(s) + CoBr2(aq)
The Correct Answer and Explanation is:
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Answer:
The pairs of reactants that will result in a chemical reaction are:
- Mn(s) + AgClO₂(aq)
- Pb(s) + Cu(NO₂)₂(aq)
Explanation
To determine whether a chemical reaction will occur between a solid metal and an aqueous solution of an ionic compound, we refer to the activity series of metals. The activity series ranks metals based on their ability to displace other metals from solution (i.e., their tendency to be oxidized). A metal that is higher in the series will displace a metal that is lower in the series from its compound in solution. This is known as a single displacement reaction.
Let’s examine each pair:
- Ni(s) + MgCl₂(aq):
Magnesium (Mg²⁺) is higher on the activity series than nickel (Ni), meaning nickel is less reactive and cannot displace magnesium from its compound.
No reaction occurs. - Pb(s) + Cu(NO₂)₂(aq):
Lead (Pb) is higher on the activity series than copper (Cu), so it can displace copper from its compound. The reaction is:
Pb(s) + Cu²⁺(aq) → Pb²⁺(aq) + Cu(s)
Reaction occurs. - Mn(s) + AgClO₂(aq):
Manganese (Mn) is much higher on the activity series than silver (Ag), so it can easily displace silver from its salt. The reaction is:
Mn(s) + Ag⁺(aq) → Mn²⁺(aq) + Ag(s)
Reaction occurs. - Pt(s) + CoBr₂(aq):
Platinum (Pt) is a noble metal and sits near the bottom of the activity series, making it very unreactive. Cobalt (Co) is above platinum, so platinum cannot displace cobalt from its salt.
No reaction occurs.
In summary, only manganese and lead are reactive enough in their respective pairs to displace the metal cation in solution. The activity series is a vital tool in predicting such displacement reactions.
