1 / 12

Equilibrium

Equilibrium. IB Textbook Chapter 15. Reversible reactions. Some reactions will take place in both directions (reactants → products and reactants ← products) The reactions occur simultaneously in both directions. Chemical equilibrium.

filia
Télécharger la présentation

Equilibrium

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. Equilibrium IB Textbook Chapter 15

  2. Reversible reactions • Some reactions will take place in both directions (reactants → products and reactants ← products) • The reactions occur simultaneously in both directions

  3. Chemical equilibrium • Equilibrium: the forward reaction and reverse reaction take place at the same rate • Aka: The Boring Point • Written like this: A + B  C • The word “rate” is important because • There is not the same AMOUNT of product & reactant • You can speed up and slow down the reaction, but it’s still going to go at the same RATE forward and backwards

  4. Keq • Equilibrium is a predictable thing • Scientists have studied equilibrium systems and determined a constant for EACH system • The call it… .Keq • K = [products]power of the # of moles [reactants]power of the # of moles • It’s often shown like this: aA + bB  cC + dD Keq = [C]c[D]d [A]a[B]b

  5. Keq Examples (more? See p. 548 #13) • Try to write K for this equilibrium: 2NO2 N2O4 Keq = [N2O4] [NO2]2 Note: K actually comes in several forms: Kc Ksp Ka Kb Kw or Kp but, you don’t need all that mess yet…

  6. Keq Examples (more? See p. 548 #13) • And this one… But, K can be a little tricky because you never include liquids (l) or solids (s): CaCl2(s) Ca2+ (aq) + 2Cl- (aq) Keq = [Ca2+][Cl-]2 • Finally… Ca(s) + 2HOH(l) Ca(OH)2(aq) + H2(g) Keq = [Ca(OH)2][H2]

  7. Interpreting K Page 548 #19 • So… What does it mean if • K < 1 • K > 1 • K = 1 Bottom of the ratio is bigger; There are more reactants than products Top of the ratio is bigger; There are more products than reactants The top and bottom are the same; The amounts of products and reactants are equal

  8. How does this fit the mini-lab? • What evidence do you have that equilibrium was achieved? • Why did the color change? • We were pushing equilibrium around, to reach a new state. • What stayed the same? • What was different?

  9. Le Châtelier’s Principle • If an equilibrium system is stressed, it will adjust/shift to relieve the stress • There are 3 ways it can be stressed • Concentration • If the con. of reactants or products is increased, the equilibrium will shift away from the increase • If the con. Is decreased, it shifts toward the decrease • Pressure • If the pressure on a system is increased, equilibrium will shift toward the side with least moles of gas • Temperature • Heat can be added or removed, and should be treated as a reactant (endothermic) or product (exothermic)

  10. Try it… NH4OH(g) + heat  NH3(g) + HOH(g) • What will happen if… • Heat is added? • The system is cooled? • More NH4OH is added? • HOH is added? • Pressure is decreased? • Volume is decreased?

  11. Le Châtelier’s Principle and K? • K can only change when • the temperature changes • the pressure changes • Changes in concentration still balance out to the same K (power point #2!)

  12. Try it…with K NH4OH(g) + heat  NH3(g) + HOH(g) • What will happen if… • Heat is added? • The system is cooled? • More NH4OH is added? • HOH is added? • Pressure is decreased? • Volume is decreased? K K K same K same K K

More Related