EK 1001 General Chemistry Question #864

[30somethingyearold]

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Hi all,

I'm sorry if this question is posted elsewhere on SDN or if this comes off as a 'stupid question' but is the following answer right to the below question:

#864 EK 1001 Gen Chem
When an atom is oxidized:
A) there is an actual transfer of electrons from the reductant to the atom
B) there is an actual transfer of electrons from the atom to the reductant
C) oxidation state of the atom decreases
D) oxidation state of the atom increases

I was confused on this because, at first, I thought it could be B) but obviously it's not a transfer to the reductant but to the oxidant, so I understand why - my question is the reasoning behind answer D) correct?
D) D is correct because "redox reactions do not represent actual transfers of electrons. For instance, the charge on an atom does not change. Instead, oxidation states represent a model to help understanding of redox reactions" - I thought the oxidized atom loses electrons to the reductant, why isn't a actual transfer of electrons?

 

[giraffesuptop]

D is correct because oxidation by definition raises the oxidation number of an atom.

B is incorrect bc there doesn't have to be a complete "actual transfer of electrons" to the reduced atom. For example, AlCl3 (lewis acid) reacts with Cl (lewis base) to form AlCl4-. In that rxn, 2 electrons from Cl form a covalent bond with Al. The electrons are not "actually transferred" completely, they are shared in the covalent bond.

In contrast, another redox rxn is Zn (s) loses 2 electrons to form Zn+2 (Zn "actually transferred electrons" to become Zn+2 in this example)

 

[cookiemonsters]

I thought the oxidized atom loses electrons to the reductant, why isn't a actual transfer of electrons?

I might be incorrect, but I think an oxidized atom loses electrons to an oxidant, not reducant. Sounds like you might have thew definitions of oxidant and reductant mixed up. B might be correct if it said "there is an actual transfer of electrons from the atom to the oxidant"

edit: there is a SDN subforum for MCAT questions here: http://forums.studentdoctor.net/forums/mcat-study-question-q-a.134/

 

[Muffinho]

I might be incorrect, but I think an oxidized atom loses electrons to an oxidant, not reducant. Sounds like you might have thew definitions of oxidant and reductant mixed up. B might be correct if it said "there is an actual transfer of electrons from the atom to the oxidant"

I'm pretty sure you're correct. An oxidant is an oxidizing agent, and a reductant is a reducing agent.

Oxidants accept elections, reductants donate electrons. A and B don't make sense based on the definitions of those words, C is obviously incorrect and D is correct by definition (and elimination).

 

[Ismet]

Moving to MCAT discussions

 

[30somethingyearold]

Thanks for your help!

 

[SN2ed]

Thread closed. These types of questions belong in the MCAT Study Q&A forum only.