Volume strength of H2O2 using iodometric titration

In summary, the conversation discusses the process of calculating the volume strength of a hydrogen peroxide solution after adding an excess acidified solution of potassium iodide. This is done by converting normality to molarity and using the equation for volume strength. The conversation also corrects a mistake in the calculation by adjusting the n-factor.
  • #1
Titan97
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Homework Statement


To a 25ml H2O2 solution, excess acidified solution of potassium iodide is added. The libereated iodine required 20ml of 0.3N sodium thiosulphate solution. Calculate the volume strength of H2O2.

Homework Equations


Normality = n-factor × Molarity
Volume strength = Molarity × 11.2

The Attempt at a Solution


I will use moles and not equivalence. But to do that, I need to convert normality to molarity.

For the reaction of sodium thiosulphate with iodine, n-factor is 2 for sodium thiosulphate.
Hence M = N/n = 0.15.
So number of milli moles of thiosulphate is 3.

$$I_2 + 2Na_2S_2O_3 \rightarrow 2Na_2S_4O_6 + 2NaI$$

So number of millimoles of iodine is ##\frac{3}{2}##.

$$2H^+ + H_2O_2 + 2KI \rightarrow 2H_2O+I_2+2K^+$$

Hence millimoles of hydrogen peroxide is ##\frac{3}{2}##

So molarity of hydrogen peroxide is ##\frac{3}{50}##

So volume strength = ##\text{M}\times 11.2 = 0.672##

But the answer given is double of what I got.
 
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  • #2
oops...
The number of electrons exchanged by 1 mole of thiosulphate is 1.
$$2e^-+2S_2O_3^{2-}\rightarrow S_4O_6^{2-}$$

Hence n-factor is 1 and not 2. Now I got the given answer.
 

FAQ: Volume strength of H2O2 using iodometric titration

What is the purpose of measuring the volume strength of H2O2 using iodometric titration?

The purpose of this measurement is to determine the concentration of hydrogen peroxide (H2O2) in a solution. This information is important for various applications, such as in the production of bleaching agents, in the medical field for wound care, and in many other industrial processes.

How is the volume strength of H2O2 measured using iodometric titration?

Iodometric titration involves adding a known amount of iodine solution to the hydrogen peroxide solution, which then reacts to form water and iodide ions. The remaining iodine is then titrated with a standardized sodium thiosulfate solution until the endpoint is reached, which is indicated by a color change. The amount of iodine used in the reaction can then be used to calculate the volume strength of the hydrogen peroxide solution.

What is the significance of using iodometric titration for measuring the volume strength of H2O2?

Iodometric titration is a commonly used method for measuring the volume strength of H2O2 because it is a relatively simple and accurate technique. It also allows for the measurement of both relatively high and low concentrations of hydrogen peroxide, making it a versatile method for various applications.

What are some factors that can affect the accuracy of the volume strength measurement using iodometric titration?

The accuracy of the measurement can be affected by factors such as the purity of the chemicals used, the presence of other substances in the solution that can interfere with the reaction, and the skill and precision of the person performing the titration.

Are there any safety precautions to consider when performing iodometric titration for measuring the volume strength of H2O2?

Yes, it is important to handle both the hydrogen peroxide and iodine solutions with care, as they can be corrosive and harmful if ingested or in contact with skin. It is also important to wear appropriate personal protective equipment, such as gloves and goggles, and to work in a well-ventilated area. Proper disposal of the chemicals and solutions used is also crucial.

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