Im stuck on this mastering chemistry problem and it seems that others are as wel

Question

Im stuck on this mastering chemistry problem and it seems that others are as well. SOme people believe that charges need to be included in the answers? Anyway:

Decide whether or not each metal dissolves in 1 M HCl. For those metals that do dissolve, write a balanced redox reaction showing what happens when the metal dissolves.

1) Zn
2) Co

Au was part of the problem as well but I already lean red that it doesn't react. ANy help would be greatly appreciated!

Explanation / Answer

(A)Zinc dissolves in HCl. Yes charges should be included in the answer. It gives us a clearer picture about which species undergoes reduction or oxidation. Zn + 2HCl -> Zn2+ + H2 +2Cl- Zinc being an active metal & above H in the electochemical series displaces H Here, Zn is oxidised to Zn2+ (loses 2 electrons) H+ is reduced to H2 (gains 2 electrons) (B) The reaction with Cobalt is a bit complex. It actually forms a complex! (a coordination compound) Cobalt (II) chloride exists as the pink hydrated complex: [Co(H2O)6]2+ under room temp conditions. When conc. HCl is added it shifts the equilibrium so that the blue [CoCl4]2- ion is formed. [Co(H2O)6]2+ + 4Cl- --> [CoCl4]2- + 6H2O This is not the typical run of the mill redox reaction. However Cobalt does in this case, dissolve in Hcl. Hope this helps

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