Question

Given the following activity series:

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Select the following elements that would react with a solution of Co(NO₃)₂.

( Hint: which elements would do the following:   A(s) + Co(NO₃)₂ --> Co(s) + A(NO₃)_x)

	A.	Cr (s)
	B.	Ag (s)
	C.	Sn (s)
	D.	Pb (s)
	E.	Mg (s)
	F.	Au (s)
	G.	Li (s)
	H.	Hg(s)

Answer 1

Au, Ag and Hg are more noble than Co and can’t reduce Co²⁺ to Co.

All other elements (Pb, Sn, Cr, Mg, Li) can be A (as a reducing agent) in the proposed reaction.

A special mention for Li. It reacts with water directly and violently (H₂ and LiOH are produced). So, for practical reasons, you have to limit the proposed list for A to Pb, Sn, Cr, Mg if the proposed reaction have to be done in an aqueous solution.