Question

Of the metals pb, mg, au, and na, which will not spontaneously donate electrons to copper in solution?

Answer 1

Au :)

Pb + Cu(2+)---> Pb(2+) + Cu
Mg + Cu(2+)---> Mg(2+) + Cu
2Na + Cu(2+) ---> 2Na(+) + Cu

Au + Cu(2+) ---> (this reaction is not possible)

Answer 2

Answer:

Au will not spontaneously donate electrons to copper in solution.  

Explanation:

Based on the activity series of metals:

K > Na > Ca> Mg> Al> Zn>Fe> Sn > Pb> H> Cu> Hg> Ag> Au  

Among the given metals Pb, Mg, Au and Na, the most reactive metals is Na, followed by Mg, Pb and Au.  All three metals Pb, Mg, and Na are above Cu in the activity series. So these metals will spontaneously donate electrons to Cu in solution. Au being lower than Cu in the activity will not spontaneously donate electrons to copper in solution.