Chemical Equilibrium Experiment


Definition of Chemical Equilibrium

Chemical equilibrium applies to reactions that can occur in both directions. In a reaction such as:

CH4 (g) + H2O (g) <–> CO (g) + 3H2 (g)

Teacher

Teacher

The reaction can happen both ways. After some of the products are created the products begin to react to form the reactants. At the beginning of the reaction the rate that the reactants are changing into the products is higher than the rate that the products are changing into the reactants.

The net change is a higher number of products. Even though the reactants are regularly forming products and vice-versa the amount of reactants and products does become stable. When the net change of the products and reactants is zero the reaction has reached balance. The equilibrium is a dynamic equilibrium. The definition for a dynamic equilibrium is when the amount of products and reactants are constant.

The objective of the experiment is to show how experimental conditions involve chemical equilibrium. The effect of the reactant concentration (CH3COO-) and the common ion addition (H+) on the reaction which is given below:

3 Fe3+ + 6 CH3COO- + 2 H2O [Fe3 (OH) 2(CH3COO) 6] + + 2 H+

A solution of the complex [Fe3 (OH) 2(CH3COO) 6] + is an intense orange. A Spectra spectrometer can be used to appraise the give up of the reaction. The higher is the absorption of the coloured complex, the higher is the absorbance of the examined solution.

The equilibrium condition is described in terms of the rate of the forward and reverse reactions for the reaction. The equilibrium constant (KP and KC) and the Law of Mass Action are introduced.

In a chemical reaction, chemical equilibrium is the state in which both reactants and products are present at concentrations which have no further inclination to change with time.  This state marks when the forward reaction proceeds at the same rate as the reverse reaction. The reaction rates of the forward and backward reactions are generally not zero but equal.  There are no net changes in the concentrations of the reactant(s) and product(s). Such a state is known as dynamic equilibrium.

Chemical equilibrium is the condition which occurs when the concentration of reactants and products participating in a chemical reaction exhibit no net change over time. Chemical equilibrium may also be called a steady state reaction. The quantities of reactants and products have achieved a constant ratio, but they are almost never equal. There may be much more product or much more reactant.

Equipment and Material 

  • Test tubes Glass-stirring rod Berol pipit
  • Syringe with cap Beakers Hot plate
  • Test tube holder hot mitts

Experiment Time taken 60 – 90 min

Chemicals taken for experiment

  • Bromothymol Blue phenolphthalein 0.1 M NaOH 0.1 M HCl

M Zn(NO3)2 15ml Club soda 6 M NaOH 6 M HCl

  • NH4Cl saturated solution Crystals NH4Cl Deionise water

Objective

This experiment is to determine the effects of disturbances on chemical systems at equilibrium. The response of the chemical systems will be necessary in terms to Lech atelier’s principle.

Discussion

Chemical equilibrium plays an important role in our lives. Many of the chemical changes involved in the metabolism of food are equilibrium-forced processes. A number of important industrial processes involve chemical reactions that do not proceed to conclusion due to back reaction. The reversibility of a reaction competes with the forward progression of a reaction. There is a point in a reaction when the products will back react to form reactant.

The extent of the reaction is 20% or 80% can be determined by measuring the concentration of each component in solution when the amount of product and reactant has stopped changing. The extent of the reaction is a function of temperature concentration ad degree of organization that is monitored by a constant value called the equilibrium constant.

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