Question

Given the following list from the activity series of metals (from most active to least active) K, Na, Al, Mn, Cr, Cd, Co, Pb, Hg which reaction would you NOT expect to occur?

1. Co²⁺(aq) + Al(s) → Al³⁺(aq) + Co(s) 2. Cd(s) + Pb²⁺(aq) → Pb(s) + Cd²⁺(aq) 3. All of the listed reactions will occur. 4. Na(s) + Mn²⁺(aq) → Na⁺(aq) + Mn(s) 5. Al³⁺(aq) + Cr(s) → Cr³⁺(aq) + Al(s)

Answer 1

5. Al³⁺(aq) + Cr(s) → Cr³⁺(aq) + Al(s)

Step-by-step explanation:

The reactions given are from a replacement. A metal that is more reactive than the other replaces it in a compound. How the metals form cations, the most reactive element must form it cation, and the element that will be replaced must form its neutral form.

So, in reaction 1, Al is more reactive than Co, so the reaction must occur; in reaction 2 Cd is more reactive than Pb, so the reaction must occur; in reaction 4, Na is more reactive than Mn, so the reaction must occur; but in reaction 5, Cr is less reactive than Al, so the reaction must not occur.