Chemical Equilibrium Presentation Part 2 c!e-γ˚T 2010
KP and KC equation Derive Kp= Kc(RT)n n = (moles of gaseous product) − (moles of gaseous reactant) If n= 0 then KC= KP n> 0 then KC< KP n< 0 then KC> KP H2(g) + Br2(g) HBr(g) N2O5(g) NO2 + O2(g) CaCO3 (s) CaO (s) + CO2(g) AgCl (s) Ag+ (aq) + Cl- (aq) (NH4)2Se (s) NH3 (g) + H2Se (g)
Solving for KC and KP Carbonyl chloride (COCl2), also known as phosgene was used in World War I as a poisonous gas. The equilibrium concentrations for the reaction between carbon monoxide and chlorine gas to form phosgene at 74oC are [CO] = 1.2x10-2 M, [Cl2] = 0.054 M, and [COCl2] = 0.14 M. Calculate KC and KP. (220, 7.6) Consider the following equilibrium process at 700oC: 2H2 (g) + S2 (g) 2H2S (g). Analysis shows that there are 2.50 moles of H2, 1.35x10-5moles S2, and 8.70 moles of H2S present in a 12.0-L flask. Calculate KC for the reaction. (1.08 x107 ) The equilibrium constant KP for the reaction 2NO2 (g) 2NO (g) +O2 (g) is 158 at 1000 K. Calculate PO2 if PNO2 = 0.400 atm and PNO = 0.270 atm. (347 atm)
Manipulating equilibrium constants Reversing a chemical equation 2NO2 (g) N2O4 (g) KC = 4.63 X 10-3 N2O4 (g) 2NO2 (g) K’C = ?
Manipulating equilibrium constants Multiplying or dividing coefficients by a constant 2NO2 (g) N2O4 (g) KC = 4.63 X 10-3 6NO2 (g) 3 N2O4 (g) K”C = ? NO2 (g) ½ N2O4 (g) K’”C = ?
Manipulating equilibrium constants Adding chemical reactions
Example 2N2 (g) + O2 (g) 2N2O (g) KC = 7.29 X 10-36 N2 (g) + O2 (g) 2NO (g) KC = 4.70 X 10-31 N2O (g) + ½ O2 (g) 2NO (g) KC = ?
Predicting direction of a reaction to achieve equilibrium K > Q, K -- > Q K < Q, K < -- Q K = Q, K < = > Q
Example The equilibrium constant for the formation of nitrosyl chloride from nitric oxide and molecular chlorine: 2NO (g) + Cl2 (g) 2 NOCl (g) is 6.5 x 104 at 35 oC. In a certain experiment, 0.02 mole of NO, 0.0083 mole of Cl2 and 6.8 mole NOCl are mixed in 2.0 L flask, in which direction will the system proceed to reach equilibrium?