Adding more of only one reactant

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Blake Ballew 1H
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Joined: Wed Sep 30, 2020 9:35 pm

Adding more of only one reactant

Postby Blake Ballew 1H » Sun Jan 10, 2021 12:34 pm

In lecture, Lavelle spoke on how if more reactant is added then more product will be formed in order to achieve the original k value. However what if in a reaction such as A+B-->C only reactant A is added. Understanding our earlier section on limiting reactions, the reaction would be unable to produce more C to achieve equilibrium as it is limited by the amount of B present. Would this in turn affect the value of k?

Andreas Krumbein 1L
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Joined: Wed Sep 30, 2020 10:00 pm

Re: Adding more of only one reactant

Postby Andreas Krumbein 1L » Sun Jan 10, 2021 1:53 pm

Yes, adding more of only a single reactant will force a shift in the concentrations since K represents the ratio between the products and the reactants. When you add more of even just a single reactant, the denominator of the equilibrium equation increases, which changes the existing ratio (Q) and forces the concentration of everything else to change in order to reestablish equilibrium.

Catie Donohue 2K
Posts: 91
Joined: Wed Sep 30, 2020 9:55 pm

Re: Adding more of only one reactant

Postby Catie Donohue 2K » Sun Jan 10, 2021 1:58 pm

I was also confused on this at first! I think it also has to do with the fact that when there is more of even one reactant (A), that reactant is therefore more likely to collide and react with other reactants to produce products. In other words, the likelihood that an A reactant will react with a B reactant increases because there are simply more A molecules to interact. I still need some more clarification about the actual mechanics of the reaction and how that yields more product, so correct me if I'm wrong.

Bhuvan Kommineni 3L
Posts: 36
Joined: Thu Dec 17, 2020 12:18 am

Re: Adding more of only one reactant

Postby Bhuvan Kommineni 3L » Sun Jan 10, 2021 2:02 pm

I agree with Andreas's response, the reaction would be at a Q value different from K, meaning that after that reactant is added the system is no longer at equilibrium. However, it is not possible for the reaction to be completely limited by B because the reverse reaction still takes place. Remember, at equilibrium the rate of the reverse reaction and the rate of the forward reaction are equal. Thus, B would still react with A to form more C and return to K from Q.

rhettfarmer-3H
Posts: 96
Joined: Wed Sep 30, 2020 9:59 pm

Re: Adding more of only one reactant

Postby rhettfarmer-3H » Sun Jan 10, 2021 7:39 pm

In terms of the formula, k=P/R. So, as you increase R It would increase P. However I would also like to know whether two reactants play a role as we learned limiting reactions in 14a. However, my basic understanding is that as long as R as a whole increase so P will decrease to balance


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