Applied Le Chatelieir's

Principle

Lesson 4

Lab 19A

Le Chatelier’s Principle

Copy the five Equilibrium Equations into your lab handout

Part I

Thymol Blue (blue) + H+ ⇌ Thymol Blue (yellow)

Fe3+(aq) + SCN-

(aq) ⇌ FeSCN2+(aq)

yellow brown

Fe3+(aq) + 3OH- → Fe(OH)3(s)

Part II

Co(H2O)62+ + 2Cl- ⇌ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

Part III

Energy + 2CrO42- + 2H+ ⇌ Cr2O7

2- + H2O(l)

yellow orange

Ba2+ + CrO42- →

BaCrO4(s)

Part IV

Cu(H2O)42+ + 2NH3

⇌ Cu(OH)2(s) + 2NH4+ + 2H2O

light blue powder blue

Cu(OH)2(s) + 4NH3 ⇌ Cu(NH3)42+ + 2OH-

powder blue violet

Part V

Application of Le Chatelier’s Principle

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orangeKnow the following:

Any acid is H+

Any base is OH-

Acids react with bases H+ + OH- → H2O(l)

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add H+

Add CrO42-

Add Cr2O72-

Application of Le Chatelier’s Principle

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orangeKnow the following:

Any acid is H+

Any base is OH-

Acids react with bases H+ + OH- → H2O(l)

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add H+

Add CrO42-

Add Cr2O72-

Application of Le Chatelier’s Principle

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orangeKnow the following:

Any acid is H+

Any base is OH-

Acids react with bases H+ + OH- → H2O(l)

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add H+

Add CrO42-

Add Cr2O72-

Application of Le Chatelier’s Principle

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orangeKnow the following:

Any acid is H+

Any base is OH-

Acids react with bases H+ + OH- → H2O(l)

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add H+ right decrease increase orange

Add CrO42-

Add Cr2O72-

Application of Le Chatelier’s Principle

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orangeKnow the following:

Any acid is H+

Any base is OH-

Acids react with bases H+ + OH- → H2O(l)

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add H+ right decrease increase orange

Add CrO42- right increase increase ?

Add Cr2O72-

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orangeKnow the following:

Any acid is H+

Any base is OH-

Acids react with bases H+ + OH- → H2O(l)

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add H+ right decrease increase orange

Add CrO42- right increase increase ?

Add Cr2O72- left increases increases ?

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

Acids react with bases H+ + OH- → H2O(l)

Stress Shift [CrO42-] [Cr2O7

2-] colour

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

Acids react with bases H+ + OH- → H2O(l)

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add NaOH

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

Acids react with bases H+ + OH- → H2O(l)

NaOH → Na+ + OH-

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add NaOH

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

Acids react with bases H+ + OH- → H2O(l)

NaOH → Na+ + OH-

spectator ion stress ion- lowers H+

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add NaOH

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

Acids react with bases H+ + OH- → H2O(l)

NaOH → Na+ + OH-

spectator ion stress ion- lowers H+

Stress Shift [CrO42-] [Cr2O7

2-] colour

Add NaOH left increases decreases yellow

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

BaCrO4 has low solubilityBaCr2O7 has high solubility

Stress Shift [CrO42-] [Cr2O7

2-] colour

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

BaCrO4 has low solubilityBaCr2O7 has high solubility

Stress Shift [CrO42-] [Cr2O7

2-] colour

Ba(NO3)2

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

BaCrO4 has low solubility- Ba2+ reacts with CrO42-

BaCr2O7 has high solubility- no reaction

Ba(NO3)2 → Ba2+ + 2NO3-

Stress Shift [CrO42-] [Cr2O7

2-] colour

Ba(NO3)2

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

BaCrO4 has low solubilityBaCr2O7 has high solubility

Ba(NO3)2 → Ba2+ + 2NO3-

stress spectator

Stress Shift [CrO42-] [Cr2O7

2-] colour

Ba(NO3)2

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange ↓ Ba2+ reacts with this ion

BaCrO4 has low solubilityBaCr2O7 has high solubility

Ba(NO3)2 → Ba2+ + 2NO3-

stress spectator

Stress Shift [CrO42-] [Cr2O7

2-] colour

Ba(NO3)2

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange ↓ Ba2+ reacts with this ion

BaCrO4 has low solubilityBaCr2O7 has high solubility

Ba(NO3)2 → Ba2+ + 2NO3-

stress spectator

Stress Shift [CrO42-] [Cr2O7

2-] colour

Ba(NO3)2 left decreases decreases yellow

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

Stress Shift [CrO42-] [Cr2O7

2-] colour

HCl

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

HCl → H+ + Cl-

Stress Shift [CrO42-] [Cr2O7

2-] colour

HCl

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

HCl → H+ + Cl-

stress spectator

Stress Shift [CrO42-] [Cr2O7

2-] colour

HCl

Application of Le Chatelier’s Principle-1

Energy + 2CrO42- + 2H+ ⇄ Cr2O7

2- + H2O(l)

yellow orange

HCl → H+ + Cl-

stress spectator

Stress Shift [CrO42-] [Cr2O7

2-] colour

HCl right decreases increases orange

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

Stress stress ion spectator ion shift colour

HCl

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

HCl → H+ + Cl-

Stress stress ion spectator ion shift colour

HCl

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

HCl → H+ + Cl-

spectator stress

Stress stress ion spectator ion shift colour

HCl

Application of Le Chatelier’s Principle- 2

Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2 + 2H2O(l)

pink blue

HCl → H+ + Cl-

spectator stress

Stress stress ion spectator ion shift colour

HCl Cl- H+ right blue

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

Stress stress ion spectator ion shift colour

Increase temperature

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

Stress stress ion spectator ion shift colour

Increase temperature

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

Stress stress ion spectator ion shift colour

↑ temp none none right blue

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

Stress stress ion spectator ion shift colour

AgNO3

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

AgNO3 → Ag+ + NO3-

Stress stress ion spectator ion shift colour

AgNO3

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

AgNO3 → Ag+ + NO3-

↑ stress- low solubility (data book-4) with Cl-

Stress stress ion spectator ion shift colour

AgNO3

Application of Le Chatelier’s Principle- 2

Energy + Co(H2O)62+ + 2Cl- ⇄ Co(H2O)4Cl2

2- + 2H2O(l)

pink blue

AgNO3 → Ag+ + NO3-

↑ stress- low solubility (data book-4) with Cl-

Stress stress ion spectator ion shift colour

AgNO3 Ag+ NO3- left pink

Here is a the first question from your lab. I will give you a good answer so that you understand the level of detail that is required in the response

1. Explain the colour changes observed when Fe(NO3)3, KSCN, and

NaOH were added to the thiocyanatoiron equilibrium system. Start by writing the equilibrium equation.

Fe3+(aq) + SCN-

(aq) ⇄ Fe(SCN)2+(aq)

yellow brown

Adding Fe(NO3)3 increases the [Fe3+] and causes the reaction to shift

right and turn brown. Adding KSCN increases the [SCN-] and causes the reaction to shift right and turn brown. Adding NaOH increases the [OH-] which reacts with Fe3+, lowering the [Fe3+] causing the equilibrium to shift left and turn yellow.