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Le Chatelier's Principle
Keq Expressions
RICE Tables
acid-base conceptual
titrations/buffers
100

According to Le Chatelier's Principle, if you add more reactants to a system at equilibrium, in what direction will the reaction shift?. What is Q in comparison to K?

the right. Q<K

100

H2(g)+Cl2(g)⇌2HCl(g)

Write the Kc expression.

Kc = [HCl]2/[H2][Cl2]

100

For the reaction

H2(g)+I2(g)⇌2HI(g)

Initially, [H2]=[I2]=1.00 M and [HI]=0.
At equilibrium, [HI]=1.60 M.
Find Kc

Kc=64

100

What is the auto-ionization of water?

Kw = 10-14

Ka • Kb = Kw

2H2O <--> OH- + H3O+

100

What is pH equal to at the half-equivalence point in a titration?

equal to the pKa

200

For the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), increasing the pressure favors the formation of what side of the equation? answer with Q vs K as well.

Products. to the right. Q<K

200

N2(g)+3H2(g)⇌2NH3(g)

Write both Kc and Kp expressions.

Kc = [NH3]/[N2][H2]3

Kp = same thing but with "P"

200

N₂O₄(g)⇌2NO₂(g)

Kc=0.25
If initially, [N₂O₄]=0.10 M and [NO₂]=0.00 M, find the equilibrium concentrations.

[N₂O₄] = 0.04625 M and [NO₂] = 0.1075 M

200

describe the pH scale

0-14

less than 7 = acidic

7 = neutral

more than 7 = basic

200

You have a buffer made of acetic acid (CH₃COOH) and sodium acetate (CH₃COONa). The  for acetic acid is . A student prepares the buffer by mixing 0.25 M CH₃COOH and 0.35 M CH₃COONa. Calculate the pH of the buffer using the Henderson–Hasselbalch equation.

pH = 4.89

300

At a certain temperature, Kc=4.0 for the reaction:

H2(g)+I2(g)⇌2HI(g)

If [H2]=0.20 M, [I2]=0.10 M, and [HI]=0.30 M,
determine Qc and predict which way the reaction will shift to reach equilibrium.

Qc=4.5

Qc>K. Shift Left

300

Write the corresponding reaction for the following Ksp expression

Ksp=1/[Pb2+][Cl-]2

Pb2+(aq) + 2Cl-(aq) <--> PbCl2

300

At 700K, Kc=54.3 for

H2(g)+CO2(g)⇌H2O(g)+CO(g)

Initial concentrations: all 0.10 M.
Predict the shift and calculate equilibrium concentrations.

shift right

[H2]=[CO2]=0.10−0.076≈0.024M

[H2O]=[CO]=0.10+0.076≈0.176M

300

Compare HCl and HClO4. Which is the stronger acid? Explain.

definition of electronegativity: how strong a particle can pull electrons towards itself. 

oxygen is very electrongative, and perchloric acid has 4 oxygens, making it more electronegative than Cl. 

this means H+ on the perchloric acid is removed much more easily, making it the stronger acid.


300

Calculate the pH of a 1.0x10-5 M solution of HNO3.

pH = 5

400

In the reaction 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) + heat, explain how the equilibrium position changes when both temperature and pressure are increased.

It shifts toward the products because of higher pressure (fewer gas moles), but back toward the reactants because adding heat favors the endothermic reverse reaction.

400


  1. H2(g)+I2(g)⇌2HI(g), K1=50

  2. 2HI(g)⇌H2(g)+I2(g), K2=?

reverse reaction 1 to get reaction 2. 

do reciprical of K1 

K2 = 1/50

400

Consider the reaction 

CO(g)+2H2(g)<-->CH3OH(g)

 A reaction mixture in a 1.00L flask initially only contains 0.185 mol CO and 0.225 mol H2. At equilibrium, 0.0521 mol CH3OH have formed. Calculate the equilibrium constant Keq for this reaction.

26.86

400

for the following compounds, write out its corresponding acid/base balanced equation (hint: add water to each one), label the acid/base and its conjugate acid/base, then name what they are (ie, H3O+ is hydronium)

1. NH3(aq)

2. HCl(aq)

NH3:

  • NH3(aq) + H2O(l) <--> NH4+(aq) + OH-(aq)
  • NH3: ammonia, base
  • H2O: acid, water
  • NH4+: ammonium ion, conjugate acid of NH3
  • OH-: hydroxide ion, conjugate base of water

HCl: 

  • HCl(aq) + H2O(l) <--> Cl-(aq) + H3O+(aq)
  • HCl: acid, hydrochloric acid
  • H2O: base, water
  • H3O+: hydronium ion, conjugate acid of water
  • Cl-: chloride ion, conjugate base of HCl
400

You mix 25.0 mL of 0.50 M Sr(OH)2 with 40.0 mL of 0.50 M HCl. Calculate pH of the resulting solution.

pH = 12.89

500

For the equilibrium

CO(g)+H2O(g)⇌CO2(g)+H2(g)

Kc=1.6×10-2 at a given temperature.
A mixture has: [CO]=0.020 M, [H2O]=0.040 M, [CO2]=0.050 M, and [H2]=0.050M.

Is the reaction in equilibrium? If not, what direction should it shift?

Q=3.125

Q>K

not in equilibrium

shift left

500

Target reaction:

C(s)+CO2(g)⇌2CO(g)

Given reactions:

  1. CO2(g)⇌CO(g)+ 1/2 O2(g), K1=1.2×10−5

  2. C(s)+O2(g)⇌CO2(g), K2=8.0×107

Calculate Ktarget

Ktarget=0.01152

500

Consider the reaction 

PbCl2(s)<-->Pb2+(aq)+2Cl-(aq) 

with Ksp = 1.17x10-5. Determine the equilibrium CONCENTRATION of Pb2+ and Cl- if you dissolve PbCl2 in a 0.100M solution of NaCl.

1.17x10-3M

500

Determine if the components of KCN are basic, acidic, or pH neutral. Then determine if the resulting solution when added to water is basic, acidic, or pH neutral. 

K+: neutral

CN-: conjugate base of weak acid HCN; accepts H+, basic

resulting solution: basic

500

pH is a concentration of Hydronium ions at ______ in a reaction.

equilibrium