roxasblade

2+ Year Member
Apr 16, 2016
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  1. Pre-Medical
A student can most effectively increase the current passing through the circuit in Figure 2 by doing which of the following?




I got the answer correct because I understand if you decrease R you would increase I

However, on one of the answer choices

How does decreasing the conc. of X^n+ & Y^m+ affect the current of the wire?
I read somewhere that it has something to do with Nernst equation, but would it decrease the current or not affect it at all, because you are decrease both the conc. of the cathode and anode

*reference for Nernst equation E= E^o -RT/nF* ln ([anode]/[cathode])
 

jackmason

2+ Year Member
Feb 21, 2018
8
21
It has to do with line notation of an EC cell:

268938

so to answer your question we just apply what we already know from Le Chatlier --> if I increase Reactants I will make more product.
Reactants = solid lead & aqueous copper ... so if increase this then i will get more of my intended product which is current :)
Their option C is wrong then. I hope someone somewhere was helped by this !! Berkeley Review helped me a ton for C/P and i initially struggled with this concept a ton. GLWS :)
 
Jul 14, 2019
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  1. Pre-Medical
It has to do with line notation of an EC cell:

View attachment 268938

so to answer your question we just apply what we already know from Le Chatlier --> if I increase Reactants I will make more product.
Reactants = solid lead & aqueous copper ... so if increase this then i will get more of my intended product which is current :)
Their option C is wrong then. I hope someone somewhere was helped by this !! Berkeley Review helped me a ton for C/P and i initially struggled with this concept a ton. GLWS :)


Actually, this question has everything to do with the Nernst equation. In addition, there is a major flaw in your argument. Pure solids and liquids do not experience concentration changes and thus have no effect on Le Chateliers principle/ on the equilibrium position of the reaction. In other words, you could add more solid, and it would have no effect. In addition, they only gave a generalized X+ and Y+. we have no clue as to what is happening at the anode or cathode, thus, we have no clue what our reactants are and what our products are. All we know is that, solids are not included in the reaction quotient, thus, Q=[X+]/[Y+] or Q= [Y+]/[X+] depending on what is oxidized and what is reduced. We can then use the Nernst equation to see how this would affect the voltage and thus the current.

Nernst equation is used for electrochemical cells that are not under standard conditions (ie. we changed the concentration). The Nernst equation is added in a picture below. If i decrease both ionic species (I assumed that they decreased them by the same amount), my reaction quotient should remain the same and thus my cell potential (Ecell) should also remain the same. So to answer OP's question, I think that the E cell and thus voltage would remain the same and thus there would be no change in the current through the system. Let me know if you agree!
Hope that helps! good luck :)

271845
 
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