Transcript Chemical Equilibrium - Green Local Schools

Chemical Equilibrium
Ch.14
(14-1) Equilibrium
• Reversible rxn in which the forward &
reverse rxns occur at = rates
• Amts. of reactants & products are
constant
Le Chatelier’s Principle
• If a system at equil. is disturbed the
system shifts to relieve the stress
• Inc. T, P, or conc. on 1 side of eq. & rxn
is forced in opposite direction
The initial soln color
(middle) is a mix of yellow &
dark red colors due to the
presence of both the Fe+3 &
the FeSCN+2 complex.
The addition of Fe+3
causes the soln to turn darker
red (left) & the removal of Fe+3
causes the soln to turn yellow
(right).
(a) Frozen N2O4 is nearly colorless. (b) As N2O4 is warmed it
starts to dissociate into brown NO2 gas. (c) Eventually the color
stops changing as N2O4(g) & NO2(g) reach conc.’s at which they
are interconverting at the same rate.
(14-2) Equilibrium Constant
• Keq: relates the conc.’s of reactants &
products
eq
Equil. Practice
A 1 L vessel contains 1.60 mols NH3, 0.800
mols N2, & 1.20 mols of H2. Calculate
Keq.
N2(g) + 3H2(g)
2NH3(g)
1. List known
[NH3] = 1.60, [N2] = 0.800, [H2] = 1.20
Equil. Practice
2. Write eq.
Keq = _[NH3]2
[N2][H2]3
3. Substitute & solve
Keq =
(1.60)2
= 1.85
(0.800)(1.20)3
Solubility Product Constant
• Ksp: expression for an ionic solid in
equil. w/ its ions in a saturated soln
Ca3(PO4)2(s)
3Ca2+(aq) + 2PO43-(aq)
Ksp = [Ca2+]3[PO43-]2
only aq & g
products
Solubility Practice
Calculate the Ksp for a 1.34 x 10-5 M
saturated soln of AgCl.
AgCl(s) Ag+(aq) + Cl-(aq)
1. List known
1.34 x 10-5 mol AgCl x 1 mol Ag+ = 1.34 x 10-5 mol Ag+
1 mol AgCl
Therefore, [Ag+] = [Cl-] = [AgCl] = 1.34 x 10-5 M
Solubility Practice
2. Write eq.
Ksp = [Ag+][Cl-]
3. Substitute & solve
Ksp = (1.34 x 10-5 )2
= 1.80 x 10-10
More Solubility Practice
Calculate the Ksp for a 6.54 x 10-5 M
saturated soln of Ag2CrO4.
Ag2CrO4(s) 2Ag+(aq) + CrO42-(aq)
Ksp = [Ag+]2[CrO42-]
= [(2)(6.54 x 10-5)]2(6.54 x 10-5)
= 1.2 x 10-12
Common Ion Effect
• Reduction in solubility of an ionic cmpd
by the addition of an ion in common w/ it