CHEM 1000 Lecture Notes - Lecture 3: Chemical Equilibrium, Reaction Quotient, Hydrogen Sulfide

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6 Apr 2016

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One of the most important things to understand about chemical equilibria is that they are dynamic, meaning that once an equilibrium is established, the reaction doesn"t stop. The compounds continue changing, but at a rate that leaves the overall concentrations equal. (1) h2 + o2 h2o (-1) h2o h2 + o2. So, using our general chemical equation, we can develop a few simple equations to determine the equilibrium constant for a reaction. aa + bb gg + hh. If (cid:449)e (cid:449)a(cid:374)t to t(cid:396)y to (cid:373)ake se(cid:374)se of these diffe(cid:396)e(cid:374)t k (cid:448)alues, (cid:449)e (cid:272)a(cid:374) say that a . Example - an equilibrium is established for the reaction shown below. Determine kc for the reaction (cid:449)he(cid:374) the (cid:272)o(cid:373)pou(cid:374)ds a(cid:396)e (cid:272)o(cid:374)tai(cid:374)ed i(cid:374) a 3. 00 l (cid:448)essel, if a(cid:373)ou(cid:374)ts of ea(cid:272)h p(cid:396)ese(cid:374)t at e(cid:395)uili(cid:271)(cid:396)iu(cid:373) a(cid:396)e . 0. 4434 g hydrogen gas 2h2s 2h2 + s2. The reaction quotient is a tool that helps us see how an equilibrium will shift if additional products/reactants are added.

Related Questions

Le Chatelierâs principle describes the way that a reaction atequilibrium will respond if that equilibrium is somehow disturbed.Imagine that you have a reversible reaction you want to performthat produces a very valuable product but the equilibrium constantfor the process is very low. Using the 3 definitions of equilibriumpresented in lecture as your framework, explain in no more than 1paragraph how the yield of reaction can be greatly increased(meaning reactants are more extensively converted into products) byapplying Le Chatliers principle.

The 3 definitions we learned in lecture:

1. rate of forward reaction= rate of reverse reaction

2. no observable change in [reactants] or [products]

3. no change in energy

I know that Le Chatliers principle states that if a system atequilibrium is disturbed, then the system will adjust so thatequilibrium can be established. I also know that if reactants aresuddenly added to a reaction already at equilibrium, then potentialenergy has effectively been added to reactant side vs. product sideof reaction. Since the system has been pushed to a higher levelthan what would be experienced at equilibrium, the reaction willproceed forwards until the lowest energy point (equilibrium) hasbeen reached. I am not sure though if this is the answer myteacher is looking for.

Does this make sense?

For a reaction aA rightarrow Products, [A]_o = 13 M, and the first two half-lives are 35 and 70 minutes, respectively, a) Write the rate law for this reaction. b) Calculate k. c) Calculate [A] at t = 335 minutes The Model of Chemical Kinetics represents the reaction rate constant as: k = (2p) times exp(-Ea/RT). What does each variable in the equation mean- that is, in regard to their contribution towards the reaction rate constant? In other words, what does each variable actually mean/refer to? Chemists commonly use a rule of thumb that an increase of 10 K in temperature doubles the rate of a reaction. What must the activation energy be for this statement to be true for a temperature increase from 63 degree C to 73 degree C? ln(k_2/k_1) = E_a/R(1/T_1 - 1/T_2) (i) What is a catalyst? (ii) What are the two types of catalysts? Explain specifically why they are different? (iii) What is one example of each type of catalyst? (i) What does it mean when a reaction is in chemical equilibrium? Specifically, within the context of reactants? products, and the forward and reverse reaction rates, what does chemical equilibrium mean? (ii) What is Le Chateleir's Principle? Within the context of reactant/product concentration, temperature, and pressure, how does Le Chatelier's Principle predict a reaction will respond to variations in reactant, product concentration, temperature, and pressure. (i) For the given reactions: N_2(g) + 3H_2(g) harr 2NH_3(g), H_2O(g) + CO(g) harr H_2(g) + CO_2(g), HCN(aq) harr H^+(aq) + CN^-(aq), 2KClO3(s) harr 2KCl(s) + 3O_2(g) and 2H_2 O(l) harr 2H_2(g) + O_2(g). Write the equation that governs each of their equilibrium rate constant K (ii) If N_2(g) + 3H_2(g) harr 2NH_3(g)'s (at 25 degree C) has K = 25, what would K be (at 25 degree C) for 2NH_3(g) harr N_2(g) + 3H_2(g)? (iii) What would K be if [5 times (N_2(g)+3H_2(g) harr 2NH_3(g)]? (i) For N_2(g) + 3H_2(g) harr 2NH_3(g): P_NH3: 1.9 times 10^-1 atm, P_N2 = 8.9 times 10^-2 atm, P_H2 = 1.9 times 10^-2 atm, what is K_p? (ii) Using K_p, calculated in the previous step, what is K at 45 degree C, where K_p = K(RT)^Delta n? (R = 0.08206 L atm/mol K). What is the difference between homogeneous and heterogeneous? (ii) If K is larger than 1, does the equilibrium life farther to the right (favoring the production of products) or to the left (favoring reactant formation)? (iii) If K is less than 1, does the equilibrium life farther to the right (favoring the production of products) or to the left (favoring the production of reactants)?

CHEM 1000 Lecture Notes - Lecture 3: Chemical Equilibrium, Reaction Quotient, Hydrogen Sulfide

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