Kinetic Study

Chemical kinetics is one of the most important and exciting domains of chemistry that studies the speeds and processes of chemical reactions. Kinetic studies may also be used to demonstrate how a chemical process’s pace can be changed. In this article, you will look at the kinetics of one particular hydrogen peroxide chemical reaction between iodide ions and hydrogen peroxide at room temperature. However, before that, let us talk about how fascinating chemical kinetics is. 

Have you ever performed titrations in chemistry labs? Seen a completely colorless solution change into a beautiful shade of burgundy or blue? Or does a coloured solution turn transparent? Amazing, right? Chemical kinetics is important to know more about the world, how it functions, why certain things happen, and provides evidence for the mechanisms of chemical processes. It is also heavily used in the pharmaceutical industry. Let us now look at how these iodide ions react by analyzing one particular hydrogen peroxide decomposition reaction to understand certain chemistry concepts. 

You come across chemical kinetics daily. The rust you see on various iron surfaces? A chemical reaction of iron when exposed to air and moisture. Digestion, photosynthesis, and combustion are other common examples. You do not see iodide ions reacting with hydrogen peroxide in day-to-day life, and this particular hydrogen peroxide chemical reaction is used to produce iodine for various purposes.

Pre-requisites

You need to know some prerequisites before you read further and understand this hydrogen peroxide decomposition reaction. Let us get you familiarized with some chemical terms first. 

Reactant, Product, And Concentration

A reactant is a chemical substance that changes when introduced or combined with other chemical substances (sodium thiosulphate in our case). There is often more than one reactant in a chemical reaction. 

On the other hand, a product is formed as a result of a chemical reaction. 

Concentration is nothing but a measurement of reactants and products, “how much” of something, in other words. There are various methods of computing concentrations, often concerning mass and volume. Standard practice is to go with the Molarity of a substance – the amount of substance per unit volume of solution. Molarity is denoted by “M”.

In this particular hydrogen peroxide chemical reaction, hydrogen peroxide and iodide ions are reactants, and iodine and water are the products. 

Rate Of A Reaction/Reaction Rate

When the concentration of a reactant or product varies at a certain rate during a specified time, this is referred to as the rate of the reaction or reaction rate.

The results of varying the concentration of Iodide ions within the reaction rate between iodide ions and the hydrogen chemical peroxide reaction at room temperature will be discussed in the subsequent section of the article.

Kinetic Energy

Motion results in the generation of kinetic energy, the energy that an object or particle has due to its movement. It is a property of a moving item or particle that is influenced by the speed and mass of the object or particle. 

Kinetic energy is equal to half of the product of its mass (m) and the square of its velocity (v). Its SI unit is Joule.

KE = ½ mv2 where,

Where KE = kinetic energy, 

m = body mass,

and v = body velocity

It is crucial to remember that this formula is applicable only for objects traveling at low-moderate speeds. As the speed increases, the very fundamental scientific concepts change. 

Oxidation, Oxidant

Oxidation is a process where a chemical substance, often a reactant, changes because of the addition of oxygen. The reactant loses some of its electrons during oxidation. Now, these free electrons are accepted by other substances that can oxidize, called oxidizing agents or oxidants.

In this hydrogen peroxide decomposition reaction at room temperature, iodide ions undergo oxidation, and hydrogen peroxide is the oxidant. 

Decomposition Reaction

A decomposition reaction is a chemical reaction in which one reactant breaks into two during a chemical reaction. This particular hydrogen peroxide chemical reaction is a decomposition reaction.

Analysis Of The Hydrogen Peroxide Decomposition Reaction

Aim

The purpose of this experiment is to determine the relationship between the variation in concentration of Iodide ions and reaction hydrogen peroxide at a certain temperature. This is intended to improve our understanding of the mechanisms and speeds of chemical reactions.

The rate of the reaction rises as the reactant concentration increases. Let us investigate the decomposition reaction to analyze the interaction between iodide ions and sodium thiosulphate in the presence of hydrogen peroxide. You will understand how reactant concentration impacts the rate of a chemical reaction.

Apparatus Required

Five 250 mL conical flasks for potassium iodide solution

Stop-watch

500 mL conical flask for hydrogen peroxide

Trough

100-milliliter measuring cylinder

A starch-based solution

Solution of potassium iodide (0.1 M)

2.5 M sulphuric acid solution

Sodium thiosulfate solution in water (0.04M)

A 3% hydrogen peroxide solution

Procedure

Take four 250 ml conical flasks and label them as 1, 2, 3 and 4.

Add 10 ml, 20 ml, 40 ml and 60 ml of 0.1 M KI solution to the flasks 1, 2, 3 and 4, respectively and add 10 ml of hydrogen peroxide to each flask as well.

Add distilled water if needed to make the volume of solution 100 ml in each flask.

Hydrogen peroxide acts as an oxidant, converting iodide ions to iodine.

H2O2 + 2l– + 2H+ → 2H2 O + l2

Add 5 ml starch solution and 10 ml of 0.04 M sodium thiosulphate solution to each flask to monitor the reaction.

Iodide ions are generated when released iodine reacts with sodium thiosulphate.

l2+ 2S2O3 2- → S4O6 2- + 2l– 

Add 5 ml of 3% hydrogen peroxide solution to flask 1 with the help of a pipette and start the stopwatch immediately. Stir the mixture and wait and observe for the blue color to appear. Note the time when the blue color appears.

After all of the thiosulphate ions have been consumed, the starch solution becomes blue.

l2 + Starch → Blue Complex 

The time needed for the blue color to appear is proportional to the reaction’s pace.

 Repeat with the solutions in flasks 2, 3 and 4. You will notice that the time is not constant. This is owing to the concentration change in each flask.

Calculation Of Kinetic Energy

To determine the total kinetic energy of an object, use the formula mentioned in the pre-requisites. The kinetic energy is equal to half of the product of its mass and the square of the linear velocity (which is centered on its mass). 

KE = ½ mv2 where,

Where KE = kinetic energy, 

m = body mass,

and v = body velocity

Use a freshly prepared sodium thiosulfate solution when performing this procedure to ensure the best possible results. The concentration of the KI solution should be greater than the concentration of the sodium thiosulphate solution to the extent that this is reasonably possible. When preparing the starch solution, use only freshly prepared solutions. 

Calculation Of The Rate Of Reaction

The rate of any chemical reaction is equal to the ratio between the change in concentration to the change in time elapsed. 

 Conclusion:

To conclude, chemical kinetics is often considered difficult due to the complex calculations involved, but it does not have to be. It is a fascinating domain of chemistry that helps you understand all the important concepts like the rate of a reaction, kinetic energy, and concentrations of the substances used. This comprehensive article on the kinetic study of the reaction between iodide ions and hydrogen peroxide at room temperature would have given you a clear intuition of the aforementioned chemistry concepts. Happy learning!