re: HSC Chemistry Marathon Archive
I don't know but here's a stab:
Because chemical reactivity, which the table of standard potential relays in order of increasing reactivity, correlates to the physical property- first ionization energy.
Zinc has a higher ionization energy than copper and thus will oxidize more readily than a metal with a lower ionization energy, in this case- Copper. Cu is more reactive than Zn and so the ability of the the Cu metal to be reduced is increased. Something like 'a more reactive metal will displace a less reactive metal in a solution of one of its salts'. Cu's higher electronegativity, ability to receive e- to fill the outer shell(?) also means that the galvanic cell works to satiate the need to fulfill the octet rule-> stability.
It's probably not right, don't hate
.
It's wrong people, the flaws have been seen. So.many.flaws. Very sorry, I should have thought out a proper answer before slashing the keyboard.
New answer:
Ionization energy also increases as you follow the periodic table from left to right across the periods and decreases going down the groups; so, from this it is correct to say that Zn has a higher ionization energy than Cu (even though they are right next to each other lol).
However, the reactivity of a metal increases as their ionization energy decreases. So Zn has a lower ionization energy than Cu which makes Zn more reactive than Cu (which would mean that Cu would oxidise more easily and Zn be reduce because it's much easier to plonk off those electrons being more reactive ;D )
But:
A negative reduction potential
(EMF (Zn)= -0.76 V): tells us that the zinc ion is
harder to reduce (is a worse oxidizing agent) than is the hydrogen ion; this also tells us that zinc metal is a better reducing agent (meaning it will, in turn,
become oxidised itself) than is hydrogen gas (every standard potential is measured against Hydrogen ( 0.00 V)
The standard reduction potential for the copper electrode is : +0.337 V:
A positive reduction potential tells us that the
copper ion can be reduced more easily (is a better oxidizing agent) than is the hydrogen ion; this also tells us that copper metal is a worse reducing agent than is hydrogen gas.
From this, it can deduced that yes, Zn> Cu in terms of reactivity (according to the periodic table and the the elements' ionization energies) but when viewed on the Standard Potentials Table, the negative reduction potential of Zn means that an electrolytic cell is required for the reaction to occur as the reaction will not occur spontaneously as a positive reducing potential (such as Cu in this case) will.
Zn being more reactive will more easily 'give-up' its electrons would make much more sense, but since the standard potentials dictates that the -/+ voltage and the reactivity series that followed from it, the opposite is true. Zn needs more energy due to its neg voltage and so is more easily oxidised than reduced.
When I said
"Cu is more reactive than Zn"I made a typo there, very sorry if I confused you; I wrote it very quickly and must of lost my train of thought- where's a periodic table and a txt book when you need one hey
. So, sub in "Zn is more reactive than Cu"
and the rest that follows is incorrect too- it's correct if you switch the elements around (like Cu where Zn is and vice versa) haha. But what I have said in terms of negative and positive reduction potentials is a better justification for the question.
A member said: "Don't metals with lower ionization energies oxidise more readily compared to metals with higher ionzation energies?"- this is completely correct and follows as a trend on the SPT, but I suppose with Zn and Cu being transition metals and only one atomic number apart there is an exception to the 'rule' due to the +/- voltage charge as explained above .
