[gt5hz]

The question involves an endothermic reaction. The reactants are A + B and the products are C + D.

Is the equilibrium equation of the reaction A + B + heat ----> C + D?

If the temperature is increased, the forward reaction will increase in rate because more temp. means more particles with enough energy for a successful reaction, so therefore the fwd. rxn will increase in rate? Is this explanation correct?

Since an increase in temp. increases the fwd. rxn and therefore causes an increase the avg. rate of decrease of the reactants, will the conc. of A + B will decrease further, and C + D will increase?

Thanks for any help. There is a question asking these same questions but for an exothermic rxn vs. PE graph, so I'd like to make sure my thought processes are correct.

[cliverlong]

The question involves an endothermic reaction. The reactants are A + B and the products are C + D.

Is the equilibrium equation of the reaction A + B + heat ----> C + D?

This is normally written

A + B C + D   :delta: H = +/- some value

Do you understand the difference between a positive and negative :delta: H  ?

there are useful formatting tools easily usable on the forum. I suggest you take time to find out what is available

If the temperature is increased, the forward reaction will increase in rate because more temp. means more particles with enough energy for a successful reaction, so therefore the fwd. rxn will increase in rate? Is this explanation correct?

Not really for the initial explantion, although changes in rate do ultimately explain the shift in equilibrium

I suggest you google "Le Chatelier's Principle" and start reading.

Since an increase in temp. increases the fwd. rxn and therefore causes an increase the avg. rate of decrease of the reactants, will the conc. of A + B will decrease further, and C + D will increase?

Thanks for any help. There is a question asking these same questions but for an exothermic rxn vs. PE graph, so I'd like to make sure my thought processes are correct.

exothermic rxn vs. PE graph

I don't know what you mean by that.

Can you post an example?

Clive

[gt5hz]

Potential Energy vs. Reaction Coordinate/Progress Graph: http://www.scienceteacherprogram.org/chemistry/nelly99img1.jpg

Yes, a negative delta H indicates an exothermic reaction, a postive delta H indicates an endothermic reaction. Thank you for the clarification about the formatting though.

Le Chatelier's Principle is on the same sheet, however, the question regarding is the last question on the page, asking to explain the state of this equilibrium when the temp. is increased. Unfortunately, I cannot use the principle to explain this question. I know that since this is an endothermic reaction, an increase in temp would cause the forward (endothermic) reaction to increase, in order to absorb this heat, so as to return to an equilibrium. I know that the PE vs. RXN COORDINATE graph for an endothermic reaction is essentially the horizontal reverse of the one posted in the link. Meaning the Ea (fwd) is more than the Ea (rev). Being that this is the case, if an increase in temp. will cause both the reactant and product particles to have enough energy for reaction, however, since the Ea (rev) is less than the Ea (fwd), the reverse reaction will be more so than the forward, as more product particles will have enough energy to react. Would something to this tune be correct?

I should have been more specific. I was on a school computer with a poor keyboard. I meant a Potential Energy vs. Reaction Coordinate graph. The initial question also starts off with this. The reason I'm asking for claification is that these 2 reactions are basically the opposite of one another so similar concepts can be used. I'd like to make sure that my application of these concepts is correct.

[renge ishyo]

Your thinking is on the right track, but I will agree with cliverlong in saying that using the idea of a "reaction rate" to describe equilibrium is a very dangerous thing. The reason being that at equilibrium the rate of the forward and the reverse reactions are equal.

It is better to discuss the relative amounts of each species at equilibrium using Le Chatelier's principle. What this principle says is that when you exert a stress on the system, the system does the opposite thing in order to minimize that stress. So if the reaction you described is endothermic from left to right, and you add energy to the system (with heat), more C+D will appear and less A+B will be present at equilibrium in order to better absorb the added energy. On the other hand if you lowered the overall energy of the system (removed heat from the system), C+D would now be decreased in order to form more A+B at equilibrium as this will release more heat into the system in the process (as the reaction from right to left, C+D to A+B, is exothermic). This is more or less what you were trying to say, but it makes no mention of the rate of the reaction.

[gt5hz]

Ah, I see. But let's disregard the law for a second, pretend it's not even applicable and look at it from a rate perspective. If the temperature is increased, the forward reaction (endothermic) will increase, due to the fact that it requires heat and adding more heat would increase the rate, due to the particle theory.

Or would the my last answer (regarding the Ea (rev) and (fwd)) be correct? Problem is they both make sense to me. o_O

Also, if this was an exothermic reaction instead, and I were to say the reverse reaction (endothermic) would be increased (heat fuels the endothermic reaction), would this shift in equilibrium when the system is heated absorb heat since it fuels the endothermic reaction? Or would it produce heat because products have been created?

[cliverlong]

(I think the following is relevant) Maybe this

http://www.chemguide.co.uk/physical/basicrates/arrhenius.html

then this

www.occc.edu/kmbailey/Chem1215/Unit3/Unit3c.ppt

The point being

As temperature rises the rate of both forward and backward reactions increase. However, the Arrhenius equation predicts the activation energy of the endothermic direction decreases proportionally more so that reaction will be proportionally quicker therefore shifting position of equilibrium until new equilibrium position is established.

Clive