1 / 11

Calculating Equilibrium Constant (Kc or Keq) Using Concentrations

This guide discusses the calculation of the equilibrium constant (K) using concentrations of reactants and products at equilibrium. Examples include determining K for specific reactions such as Br2 + F2 ↔ 2BrF and N2 + 3H2 ↔ 2NH3, showcasing stoichiometry's role in finding final concentrations. Detailed sample problems illustrate how to compute K from equilibrium concentrations. The guide concludes with practice questions to enhance understanding of equilibrium dynamics and Kc calculations.

kesia
Télécharger la présentation

Calculating Equilibrium Constant (Kc or Keq) Using Concentrations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Calculating Kc or Keq Chapter 13 Pg 499-508

  2. In order to calculate the value of K, we need to know the concentration in mol/L of all reactants and products at equilibrium. • Sometimes we do not immediately know all of the concentrations at equilibrium, but we are given enough information to determine all of the concentrations at equilibrium and then K.

  3. For Example 0.100 mol/L Br2 and 0.100 mol/L F2 were initially mixed together and allowed to come to equilibrium according to the following reaction: Br2(g) + F2(g) <-->2BrF(g) At equilibrium the concentration of Br2 was found to be 0.00135 mol/L. Calculate the value of K.

  4. Fill this in…

  5. Should Look like:

  6. Good ol’ Stoichiometry • We used stoichiometry (the relationship with the balanced chemical equation to help us solve for the final concentrations) • Since Br2 and F2 were a 1:1 mole ratio and had the same initial concentration, they would have the same final. • But BrF was a 1:2 mole ratio with Br2, so we had to double the change in concentration and therefore the final answer.

  7. We’re not finished! • Now we can solve for K because we found the final concentrations (at equilibrium) • K =[BrF]2 / [Br2][F2] =[0.1973M]2/ [0.00135M][0.00135M] =2.15 x 104

  8. SAMPLE PROBLEM 1 The following concentrations were found at equilibrium for the reaction: N2(g) + 3H2(g)<--> 2NH3(g) [N2] = 0.25 M; [H2] = 0.45 M; [NH3] = 0.60 M Calculate K. Answer: K=16

  9. Sample Problem 2: A closed container initially had a CO(g) concentration of 0.750 M and a H2O(g) concentration of 0.275 M. It was allowed to reach equilibrium. At equilibrium, analysis showed a CO2(g) concentration of 0.250 M. The equationfor the reaction is: CO(g) + H2O(g) <-->CO2(g) + H2(g) Calculate K Answer: K=5.00

  10. SAMPLE PROBLEM 3 A closed chemical system initially contained 6.0 M SO2; 2.5 M NO2; and 1.0 M SO3. Equilibrium was eventually reached for the reaction SO2(g) + NO2(g)<--> SO3(g) + NO(g) At equilibrium, the container was found to have 3.0 M SO3 present. Calculate K. Answer: K=3.00

  11. Homework: • Work on questions 11&12 pg. 508 (practicing with Kc) • Tough questions: Pg 515 #25-29

More Related