Chemistry Study Note - Rice Charts, Haber-Bosch Equilibrium

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Write the chart that will help
H
(g)
I
(g)
HI(g)
2
2
determine equilibrium [ ]s for the
Mole ratio
1
1
2
reaction H
(g) + I
(g)
2HI(g),
[Initial] (M)
0
0
7.5
2
2
given an initial [HI] of 7.5 mol/L.
[Change] (M)
+ x
+ x
- 2x
[Equilibrium] (M)
x
x
7.5 - 2x
What simplification is often helpful
When Kc is very small we can often assume that changes in
when solving Kc problems?
concentrations are negligible.
In the equation x(1-x), if x is very
Only the x in the brackets is considered negligible.
small, can we assume that x is
General Rule: A small x can be ignored when adding or subtract-
negligible? Give the general rule.
ing. A small x cannot be ignored when multiplying or dividing.
Demonstrate that a small x can be
Let’s use x = 0.00001 as an example of a value for x that is small
ignored in addition and subtraction
relative to 0.3. Solving for what’s inside the brackets we get
but not in multiplication or division.
0.3 + 2x = 0.30002 (which is very close to 0.3). However,
Use x(0.3+2x) as an example.
x(0.3) = 0.00003 (which is very different than 0.3).
You should be able to solve problems similar to examples 14.7 - 14.10
11.3
Distinguish between molecular,
Molecular: the typical way to write a reaction with compounds
ionic and net ionic equations.
and their states. Ionic: similar to a molecular equation except that
aqueous compounds are written as ions. Net ionic: similar to ionic
except that unreacted chemicals are removed from the equation.
What conditions must be met in all
Materials balance (equal numbers of all atoms on left and right),
types of chemical equations?
Electrical balance (equal numbers of charges on left and right).
Write ionic and net ionic equations
Ionic:
S(aq) →
(aq) → CdS(s) + 2Na
2+
-
+
2-
+
-
Cd
(aq) + 2NO
(aq) + 2Na
(aq) + S
(aq) + 2NO
(aq)
for Cd(NO
)
(aq) + Na
3
3
3
2
2
Net ionic:
CdS(s) + 2NaNO
(aq)
3
(aq) → CdS(s)
2+
2-
Cd
(aq) + S
How can the charge on an ion be
The charge is equal to the valence of the ion. For ions that consist
determined?
of one atom, the position on the periodic table is often instructive
(e.g. Na is in group IA; it loses one electron to become 1+).
Valences of polyatomic ions can be referenced on pg. 71.
Also, if you know the charge on one ion you can figure out the
charge on the other. For example, since Na
S(aq) is neutral and
2
+
Na
becomes 2Na
, S must have a 2- charge.
2
Pg. 692-3
Write the balanced equation for the
N
(g) + 3H
(g)
2NH
(g) + heat
2
2
3
production of ammonia gas.
Or
(g) ΔH° = -90 kJ
Indicate if it is endo- or exothermic.
N
(g) + 3H
(g)
2NH
2
2
3
Name the process used today to
The Haber process or the Haber-Bosch process.
manufacture ammonia?
Under what conditions of
High pressure (200 atm) and moderate temperature (400°C). High
temperature and pressure is this
pressure shifts the equilibrium to the right. A high temperature
process carried out? Why?
actually favors the shift away from NH
formation. However a
3
high temperature is needed to increase the reaction rate.
What other factors ensure a high
The presence of catalysts and the removal of NH
via
3
yield of ammonia?
condensation. (Removing NH
continuously shifts the equilibrium
3
to the right, favoring the production of ammonia).
What principle does the Haber
Le Chatelier’s principle.
process demonstrate?

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