Chemical Equilibrium + Acids & Bases PDF

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Summary

Study guide for equilibrium and acids and bases...

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Chemical Equilibrium - Reaction at equilibrium: R ⇆ P - The concentrations of Reactants and Products are constant - Rate of forward reactions = rate of reverse reactions - Because of these two ideas → under same conditions reaction at equilibrium has same product over reactant ratio - This ratio is called the equilibrium constant, Kc< - Do not include units in the equation since the concentrations are approximations - Chemical activity doesn’t have units - Example: N2 (g) + 3H2 (g) ⇆ 2NH3 (g) at 500 degrees celsius - [NH3]2 / [N2] [H2]3 = Kc - If the reaction is reversed → 2NH3 (g) ⇆ N2 (g) + 3H2 (g) → 1/Kc - If all reactants and products are in same phase = homogeneous equilibrium - If one or more R and P are in different phase: heterogeneous equilibrium - Molar concentrations of a pure substance (solid or liquid) doesn’t change in a reaction → not include in Kc expression - Example: Ca(OH)2 (s) ⇆ Ca2+  (aq) + 2OH- (aq) → Kc = [Ca2+  ] [OH- ]2 - For a gas we use its partial pressure (P) and equilibrium constant is denoted as Kp - CaCO3 (s) ⇆ CaO (s) + CO2 (g) → Kp = [Pco2  ] - Often K is used to represent Kc or Kp - How to convert between partial pressure and concentration for a gas - Use ideal gas law → PV=nRT → P/RT= n/V - For concentration to partial pressure → nRT/V=P - For pressure into concentration P/RT=n/V -

Extra notes - Spectator ions are not included in the equilibrium expression - 10^5 Pa= 1 bar - If you are at equilibrium with concentration used and you add moles of a substance - You first have to see the added concentration (divide moles by volume) - Then add it with the equilibrium concentration of the same substance - Then set up an ice table with -x and +x values - If you add HI to the H2 + I2 -- 2HI place then there will be a an equilibrium shift to the left so ice table will be: +x +x -2x - Solvents are not included in the equilibrium constant expression - Equilibrium constants are useful because - They indicate the extent to which a reaction progresses to completion - The relative concentrations of products and reactants - Kc represents the equilibrium constant expression using the equilibrium molar concentrations of the products and the reactants

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Kp represents the equilibrium constant expression using the equilibrium partial pressures of the reactants and products K and what it tells us - If K> 103 then reaction almost goes to completion before reaching equilibrium - Strongly favors product, more products than reactants, lies to the right - If K< 10-3  then equilibrium is reached relatively quickly - Strongly favors reactants, more reactants than products, strongly lies to the left, - If K> 1 then equilibrium lies to the right but not strongly. Equilibrium concentrations of product is greater than equilibrium concentrations of reatant - If K...