Question

What is titration and why titrations are useful?

Answer 1

Titration is a technique of quantitative analysis. In this, we use a solution of known concentration as titrand. To this a solution of unknown concentration (called titrant) is added. We use the chemical equation for the reaction between the titrand and titrant and find out the number of moles of titrand reacting with the titrant. And thus by equating the number of moles of titrand reacting with those of the titrant we can find the concentration of solution with unknown concentration.

Number of moles=Molarity x volume (L)

To know exactly how much titrant is required to completely react with the titrand, we make use a substance called indicator which changes colour once the reaction is complete and just one more drop of titrant is added.

Suppose we have HCl solution with a known concentration and NaOH with unknown concentration. Their reaction is as shown

So one mole HCl reacts with 1 mol NaOH

Number of moles of HCl=number of moles of NaOH

Molarity of HCl x Volume of HCl = Molarity of NaOH x volume of NaOH

We take a known volume of HCl in a conical flask. To this few drops of an indicator like phenolphthalein can be added followed by addition of NaOH solution from buret dropwise, swirling the conical flask. The reading when the colour of HCl solution changes to permanent light pink is called the end point and is recorded. We have to stop the addition of NaOH after that. To maintain precision, three concordant readings are taken by repeating the experiment. Thus, we can find the concentration of NaOH solution. Titrations are used to find concentration of a solution using solution with known concentration.