DAT Destroyer GC #222

[Strag]

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2011 Version.

Consider the rxn A+ B->C

Which does not affect the rxn rate of this irreversible rxn?

a decreasing a
b increasing b
c adding catalyst
d removing c
e increasing temp

Ans is D

Why is it not A? I'm going by Le Chatlier's principle...if you decrease [A], it would push the rxn to go left, but the reaction is irreversible (meaning it cannot go left...right?).

Whereas if you remove C, wouldn't that make the rxn go more right to make more C since [C] is being removed?

 

[casper22]

2011 Version.

Consider the rxn A+ B->C

Which does not affect the rxn rate of this irreversible rxn?

a decreasing a
b increasing b
c adding catalyst
d removing c
e increasing temp

Ans is D

Why is it not A? I'm going by Le Chatlier's principle...if you decrease [A], it would push the rxn to go left, but the reaction is irreversible (meaning it cannot go left...right?).

Whereas if you remove C, wouldn't that make the rxn go more right to make more C since [C] is being removed?

Since it is irreversible reaction, changing A and B will affect the reaction rate as they are the reactants.

Whereas, if you change C, the reaction will shift right to make more C, this is where the irreversible part mainly comes in, since its irreversible, even if the concentration of C decreases, it will have no effect on the reaction since C is always the product..

Hope this makes sense...

 

[yueru]

This is how I solve this problem: rate=K [A] (not necessary the second order, just an example)...only change of concentration of A or B will change rate.

 

[Strag]

Since it is irreversible reaction, changing A and B will affect the reaction rate as they are the products

Whereas, if you change C, the reaction will shift right to make more C, this is where the irreversible part mainly comes in, since its irreversible, even if the concentration of C decreases, it will have no effect on the reaction since C is always the product..

Hope this makes sense...

How are A and B products? It says in the explanation that C is a product.

 

[casper22]

How are A and B products? It says in the explanation that C is a product.

My bad..i meant reactants... I will edit it....

 

[FROGGBUSTER]

You use Le Chatelier's in dealing with thermodynamics & equilibrium. This is a kinetics problem.

Also, the rate of this reaction depends only on concentration of reactants because it's one direction only.

 

[Strag]

You use Le Chatelier's in dealing with thermodynamics & equilibrium. This is a kinetics problem.

Also, the rate of this reaction depends only on concentration of reactants because it's one direction only.

Thanks for explanation I understand it now