The Effects of Equilibrium in the Solution Quantitatively Followed Le Chatelier’s Principle

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CHM 420

Experiment 5 : Chemical Equilibrium

Name : Nur Syaza Hani Binti Nick Hamasholdin

Laboratory partner’s name : Nurul Fakhirah Binti Mat Azam

Class : AS2461B

Lecturer’s name : Dr. Zainiharyati Bt Mohd Zain

Date of the laboratory experiment  : 18th October 2018

TITLE: EXPERIMENT 5 – CHEMICAL EQUILIBRIUM

OBJECTIVE

To observe the effects of equilibrium in the solution quantitatively followed Le Chatelier’s principle.

INTRODUCTION

Chemical equilibrium is a state in which there are no observable changes as time goesxby. It is calledxequilibrium when the rates of forward and reversexreaction are equal and the concentration of the reactants and products remain constant. Many other changes are reversiblexreaction which can be shown by sign ⇌. The reaction does not stop when equilibrium is reached because the reaction is still going on at the same rate as each other. When a chemical system atxequilibrium is subjected to axstress, the system will return to equilibrium byxshifting to reduce the stress.

Le Chatelier’s principle states that when a system in chemical equilibrium is disturbed by a change of temperature, pressure, volume or concentration, the system shifts in equilibrium composition in a way that tends to counteract this change of variable. This principle is used to predict the direction or shift of the equilibrium position when stresses are introduced. For concentration, adding more reactant will produces more product, and removing the product as it forms will produce more product.

 [Reactants] – shifts right to favor products[pic 2]

 [Products] – shifts left to favor reactants[pic 3]

CHEMICALS & APPARATUS

• Concentrated ammonium hydroxide (NH4OH)
• 0.1 M cobalt(II) chloride (CoCl2)
• 0.1 M iron(III) chloride (FeCl3)
• 12 M hydrochloric acid (HCl)
• 0.1 M copper(II) sulfate (CuSO4)
• 6M ammonium hydroxide (NH4OH)
• Phenolphthaleinx
• 0.1 M potassiumxthiocyanate (KSCN)
• 0.1 M silverxnitrate (AgNO3)
• 3 M sulfuricxacid (H2SO4)

PROCEDURE

Part A : iron(III) chloride, FeCl3 + potassium thiocyanate, KSCN

1. A stockxsolution is prepared by adding 1xml of 0.1xM iron(III) chloride and 1 ml of 0.1 M potassiumxthiocyanate solution into 50 mlxdistilledxwater. The solution is mixedxthoroughly. 5 ml of this stock solution is poured into four test tubes that are labelled as 1, 2, 3 and 4.

• Test tube 1 : Act as control for colorxcomparison.
• Test tube 2 : 1 ml of 0.1 M iron(III) chloride solution. The color change is observed.
• Test tube 3 : 1 ml of 0.1 M potassium thiocyanate solution is added and the color change is observed.
• Test tube 4 : 0.1 M of silverxnitrate solution is added drop by drop (less than 1 ml) until the color of the solution isxdischarged. A white precipitate is formed. The solution and its precipitatexis poured half into another test tube. 0.1 M of potassiumxthiocyanate solution is added dropwisexto one tube and 0.1 M iron(III) chloride solution to another. The observable changes are recorded.

Part B : copper(II) sulfate, CuSO4 + ammonia,NH3

1. 2 ml of 0.1 M copper(II) sulfatexsolution is placed into two test tubes:

• Test tube 1 : Act as control for color comparison.
• Test tube 2 : 6 M of NH3 solution is added drop by drop. The solution is shake after each drop added. The color change is recorded. NH3 is added continuouslyxuntil another color change. 3 M of H2SO4 is added dropwise until the color change back to itsxoriginal.

Part C : cobalt(II) chloride solution

1. 1.4 ml of 0.1 M cobalt(II) chloridexsolution is added into each three test tubes:

• Test tube 1 : Acts as control.
• Test tube 2 : 3 ml of HCl is added drop by drop and the changes is recorded. Distilled water is then addedxdropwise until that solution returns to its original color.
• Test tube 3 : Half ofxspatula of  solid ammoniumxchloride is added into the test tube. The tube has shaken well and a saturatedxsalt solution is formed.

1. Test tubex1 and 3 are put into a water bath and shaken occasionally. The color changes are noted.

1. Both tubes are cooled under tapxwater until original color is obtained.

Part D : Ammonia solution

1. An ammoniaxstock solution is prepared by adding 5 drops of 6 M ammonia and 3 drops of phenolphthaleinxinto 50 ml of tap water and mixed. 5 ml of the stock solution is poured into each three test tubes.

• Test tube 1 : Act as control.
• Test tube 2 : A very small amount of solidxammonium chloride is dissolved in the stock solution and the result is observed.
• Test tube 3 : A few drops of 6 M hydrochloricxacid is added to the stock solution and mixed. The observable changes is recorded.

DATA

A : iron(III) chloride, FeCl3 + potassium thiocyanate, KSCN

The ionic equation :            Fe3+(aq) + SCN-(aq) ⇌ Fe(SCN)2+(aq)

                                              Pale yellow      Colourless             Red