TBR Gen Chem Ch4 #65

[vpanopoulos]

The question states: "Which of the following metals can be oxidized by gastric fluid?"
A) Copper
B) Gold
C) Silver
D) Zinc

The answer is D, Zinc.

When I first approached this question, I understood that for a transition metal to become oxidized, it needs to lose its electrons very easily. Therefore, the metal with the LOWEST ionization energy will be oxidized by gastric fluid (strong acid).

Wouldn't the answer be Gold, because it is furthest down on the periodic table whereas Zinc is the metal with the highest ionization energy?

Thank you!!

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[dudewheresmymd]

I think they may have been referring to the reactivity of metals here... in general copper, gold, silver are not very reactive with acid or water...was this a discrete or did they provide an accitity series? I don't see it in my version.

http://en.wikipedia.org/wiki/Reactivity_series

 

[sazerac]

The question states: "Which of the following metals can be oxidized by gastric fluid?"
A) Copper
B) Gold
C) Silver
D) Zinc

The answer is D, Zinc.

When I first approached this question, I understood that for a transition metal to become oxidized, it needs to lose its electrons very easily. Therefore, the metal with the LOWEST ionization energy will be oxidized by gastric fluid (strong acid).

Wouldn't the answer be Gold, because it is furthest down on the periodic table whereas Zinc is the metal with the highest ionization energy?

Thank you!!

This might be a "common sense" kind of question... the reason we use copper, silver, and gold as money is that they will not dissolve in the presence of H+ ions which can be found in acids and even in water.

 

[Odi]

This is thoroughly explained by electrochemistry.

Gold, silver, and copper all have positive reduction potentials. H+ has a standard reduction potential of 0. Zn has a negative reduction potential meaning it will oxidize readily in an H+ solution. Applying trends to transition metals is a little tricky.

It's important and easy to remember that our valuable metals (platinum, gold, silver, copper etc) do not oxidize readily and remain in their metallic form.

 

[vpanopoulos]

Ok Cool!! Everyone's answer helped, thank you!

 

[plage noire]

I figured that Cu/Ag/Au would be readily oxidized based on their electron configurations: __d10__s1 and that they would readily give up that 1 s electron to be more stable (whereas Zn is [Ar]3d104s2. I understand the "common sense" approach that gold, silver, and copper are less reactive - how would I have approached this from a chemistry standpoint that would indicate to me that zinc has negative reduction potential (without memorizing that)?