1. “Ice, ice, baby…” (2) If you know the concentrations
of only some substances at
equilibrium, make a chart and
use reaction stoichiometry to
figure out the other concentrations
at equilibrium. THEN plug and chug.
“What kind of chart?”
“Ice,
ice,
baby…”
I = “initial”
C = “change”
E = “equilibrium”

2. At 1000 K, the amounts shown below are known.
Find 1000 K.
2 SO3(g) SO2(g) O2(g)
initial x 10–3 M M M
D –3.65 x 10–3 M x 10–3 M x 10–3 M
at eq x 10–3 M x 10–3 M x 10–3 M
Put “at eq.” #s into Kc expression…
= x 10–3

3. By knowing K, we can...
(1)
predict the direction of a reaction
(2)
calc. amts. of R and P once eq. has been
reached, if we know init. amts. of everything
reaction quotient, Q: what you get when you plug the
R and P amts. at any given time
into the eq.-constant expression
If Q > K...
rxn. proceeds
If Q < K...
rxn. proceeds
If Q = K...
we are at eq.

4. For H2(g) + I2(g) 2 HI(g), Kc = 51 at a temp.
of 488oC. If you start with mol HI, mol H2,
and mol I2 in a 2.0-L container, which way will
the reaction proceed?
(need more
product)
= 1.3
< 51
HI!
rxn. proceeds to eq.
From an MSDS for HI(aq)… (i.e., hydroiodic acid)
“May cause congenital malformation in the
fetus. Corrosive - causes burns. Harmful if
swallowed, inhaled, or in contact with skin.
Very destructive of mucous membranes. May
affect functioning of thyroid. May increase size of skull.”

5. For PCl5(g) PCl3(g) + Cl2(g), Kp = 0.497 at
500 K. At equilibrium, the partial pressures of PCl5
and PCl3 are atm and atm, respectively.
Find the partial pressure of Cl2.
1.22 atm

6. For the reaction in the previous problem, if a gas cylin-
der at 500 K is charged with PCl5 at 1.66 atm, find the
partial pressures of all three substances at equilibrium.
PCl5(g) PCl3(g) Cl2(g)
initial atm atm atm
D –x x x
at eq – x x x
x = atm or –1.190 atm a b c