Unit 11. Equilibrium. Dynamic balance. Reactions go to completion when almost all reactants convert to products. (most reactions don’t go to completion) Reversible reactions: occur in both forward and reverse directions (double arrow is used ) N 2 + 3H 2 2 NH 3
N2 + 3H2 2 NH3
aA + bB cC + dD
keq > 1 : products are favored at equilibrium
keq < 1 : reactants are favored at equilibrium
H2 (g) + I2 (g) 2HI (g)
Keq = [HI]2
keq = [I2 (g)]
[I2(s) ] *concentrations of solids and liquids are constant so they are combined with keq
Keq = [I2(g)]
Each of these will now be discussed in detail
N2(g) + 3H2(g)↔ 2NH3(g)
Ex. At a temperature of 1405K, hydrogen sulfide which has a foul odor resembling rotten eggs, decomposes to hydrogen and diatomic sulfur. The equilibrium constant for the reaction is 2.27x10-3.
2H2S (g) 2H2 (g) + S2 (g)
What is the concentration of hydrogen gas, [H2 ] , if [S2 ] =0.0540mol/L and [H2S] = 0.184 mol/L?
Mg(OH)2(s) Mg2+ (aq) + 2OH – (aq)
For NaCl : ksp=[Na+ ][Cl– ]
For Mg(OH)2 :ksp= [Mg2+ ][OH –]2
ksp=[Ag+ ][I – ]
ksp= 8.5x10-17 at 298 K
What is the solubility of AgI? (for every mole of AgI that dissolves, an equal number of Ag+ ions and I – ions forms.)
[Ag+ ][I – ] = 8.5x10-17
Ex. The Ksp for silver carbonate, Ag2CO3, is 8.4x10-12 at 298K. What is the concentration of the silver ions, Ag+ ions?