Question

steps involved in volumetric analysis

Answer 1

Techniques for Volumetric Analysis: 
Volumetric analysis involves measuring the volumes of two solutions that react together. 
The basic principles are as follows. 
• The solution to be analysed contains an unknown amount of the chemical A. 
• Reagent B, of known concentration, reacts with chemical A, usually in the presence of 
an indicator to show the end-point, i.e. when the reaction is complete. 
• The volumes of solution and reagent needed to complete the reaction are measured 
accurately, by performing a titration. 
• The volume and concentration of reagent B used in the titration give the amount of B 
(in moles). 
• Using the mole ratio given by the equation, the amount of chemical A in the measured 
volume of solution is deduced. 
• From this, the amount of A in the original sample is calculated. Titrations usually follow the same series of steps: 
1. Clean the pipette, and rinse it with a little of the solution to be used. 
2. Clean a conical flask, using distilled or deionised water for the final rinse. The flask 
does not need to be dry. 
3. Pipette the specified volume of one reactant into the flask, touching the nozzle 
against the flask to deliver the correct volume. (Do not blow out the small amount 
of liquid remaining in the nozzle.) 
4. Rinse the liquid down the flask 
wall into the bottom with a little 
distilled water from a wash bottle. 
(Remember, diluting the solution 
does not alter the measured 
amount of reactant in the flask.) 
5. Add the indicator if required. 
6. Clean the burette, and rinse it with 
a little of the second reactant 
solution. 
7. Fill the burette, including the jet 
below the tap. The liquid level 
does not need to be exactly on 
zero. 
8. Note the reading at the bottom of 
the meniscus. 
9. Perform a preliminary (rough) 
titration by running the solution 
from the burette into the flask, 
while swirling the mixture, until the 
end-point is reached. Turn the 
burette tap with your left hand, 
while swirling the flask with your right. (If left-handed, do the reverse.) 
10. Read the meniscus again. Subtract the first reading, to give the volume added. 
This is the rough titre. It is too high, because you have gone past the end-point. 
11. Repeat steps 2 to 5. (You can use the same flask again.) 
12. If the liquid level is more than half way down the burette scale, fill it up again. 
13. Read the burette, then perform an accurate titration by running the solution into the 
flask, with swirling, until you have added about 3 cm3 
less than the rough titre. 
14. Continue by adding a few drops at a time, swirling after each addition. When the 
colour begins to change, indicating that you are near to the end-point, add one 
drop at a time. 
15. Stop as soon as the end-point is reached. If in doubt, read the burette, then add 
one more drop. If the colour now indicates that you have gone past the end-point, 
use the previous reading. If not, continue adding single drops until it does. 
16. Subtract the initial reading from the end-point reading to give an accurate titre. 
17. Repeat the accurate titration (steps 11 to 16) twice more. The titres should agree 
within ± 0.1 cm3 
; if not, repeat again. 
18. Take an average of your three accurate titres. Use this as the 'volume added' in 
your calculate.

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Answer 2

Procedure of volumetric analysis

Volumetric analysis. Volumetric analysis is an analytical method or procedure for working out the titre or concentration of an analyte in a solution. This is done by measuring the volume of a standard solution of an appropriate reagent whose precise concentration is already known. ... This technique is known as titration.