Quantitative and Qualitative Analysis:Acid -Base Titration

Quantitative and Qualitative Analysis:Acid -Base Titration

Qualitative analysis deals with the identification of elements present in a given sample of a substance, whereas Quantitative analysis involves the calculation of the amount or quantity of an element or compound present in a given sample.

There are basically two approaches to quantitative analysis, which are volumetric and gravimetric analysis. The volumetric analysis is directly involved with the volume measurement of a substance and gravimetric analysis
deals with direct mass measurement. In volumetric analysis, we have titration experiment.
TERMS TO UNDERSTAND:Standard solution, mole, morality, amount,Acid and Base.
Conjugate Acid  –
A molecule that can be described as a base that has gained one proton.
Conjugate Base  –
A molecule that can be described as an acid that has lost one proton.
Endpoint  –
The volume or amount of acid or base added to a solution to neutralize the unknown solution during a titration. When using an indicator, the endpoint occurs when enough titrant has been added to change the color of the indicator.
Equivalence Point  –
The volume of titrant and pH at which the amount of acid equals the amount of base present in the original solution, or the amount of base equals the amount of acid present in the original solution.
Indicator  –
A molecule whose conjugate acid or conjugate base has a different color. An indicator is used to mark a certain pH level.
pH  –
A measure of the hydrogen ion concentration, it is equal to – log [H+]..
Strong Acid  –
An acid with a pK a less than zero. Strong acids completely dissociate in water.
Strong Base  –
A base with a pK b less than zero. Strong bases completely dissociate in water.
Titrant  –
The acid or base of known amount and concentration that is added to the unknown solution during an acid-base titration.
Titration  –
An experiment where an unknown concentration of acid or base is neutralized with a known volume and concentration of acid or base to determine the concentration of the unknown.
Titration Curve  –
A plot of solution pH versus titrant volume during a titration.
Weak Acid  –
An acid with a pK a greater than zero. Weak acids do not completely dissociate in water.
Weak Base  –
A base with a pK b greater than zero. Weak bases do not completely dissociate in water.

Titration  as described previously here is a quantitative approach to volumetric analysis, it is an experimental procedure in which a solution – called the titrant – whose concentration is accurately known from a graduated vessel(burette) is added to a known volume of a solution with unknown concentration – called the analyte until the chemical reaction between the two is just completed.

In carrying out Acid -base titration in the laboratory, the materials and precautions involved are as follows


1. Weighing bottle 
2.  Chemical balance 
3.  Pipette 
4.  Burette
5.  Retort stand 
6.  Clamp stand 
7.  Funnel 
8.  White tile
9.  Conical flask 
10.Standard volumetric flask
11.Filter paper 
 Precautions when using the Burette 
 1. Rinse the inside of a clean burette thoroughly with the solution it will contain after you must have rinse it with distilled water and allow to dry.
2. Allow the solution to run out through the stopcock. Drain the burette completely. Repeat the rinsing at least once.
3. Make sure the outside of the burette is clean and dry, and then mount it securely to a laboratory clamp stand using a burette clamp of the proper size.
4. Fill the burette to the zero mark, using a graduated cylinder, small beaker, flask or other container. Use a funnel if necessary to prevent spillage.
5. Carefully run some solution through the stopcock to fill the burette tip completely, making sure there are no air bubbles and that the level of the solution falls to or below the zero. Meniscus  mark.
6. Record the starting volume. When you complete the titration, you will subtract the starting volume from the final volume to determine the amount of solution you have added. (Read the volume from the bottom of the burette.
7. Remove the funnel after taking your reading 7. Try to avoid inconsistent burette readings
Precautions when Using pipette
 1. Carefully rinse the pipette with the solution to be contained (Base) after you might have rinsed it with distilled water
2. Avoid air bubbles in the pipette
3.Make sure the mark to be read is at the level with your eyes
4.Do not blow the last drop on the pipette
 Precaution When Using Conical Flask
  1. Do not rinse it with any of the solution used in the titration process except distilled water
2. Carefully wash down with distilled water any drop of the solution that sticks by the side of the conical flask during titration.In a titration experiment to determine the Concentration  of sodium hydroxide Solution using
Hydrochloric acid , carefully follow the process below

1.Fill the burette with hydrochloric acid solution that has been standardized and adjust its level to the zero mark.
2. Pipette 2cm3 of the sodium hydroxide solution into the conical flask ( try to use pipette filler, but in case of absence, use your mouth to suck the base into the conical flask3.Add two drops of methyl orange indicator the
colour should turn pink.
Carefully dispense the acid solution from the burette above into the alkali solution and swirl the flask after each addition to enable equal and proper mixture of the two solutions
5.Continue the process until the end point is reached, when the indicator turns orange.
6. Note the volume of the acid used to neutralize the alkali and record the final
volume obtain.
7. The first titration is usually an approximate value, turn or discard your first titre value and carry out two more accurate titration
8. When approaching the end-point, add in the acid drop by drop until one drop of the acid changes the colour of the indicator permanently.
Then record the burette readings. I hope this post help you in your titration endevour

1.      A is a solution of HCL containing 7.30 g/dm3. B is a solution of Na2CO3 containing
10.6g/dm3. Put A in a burette and titrate against 20.0cm3 portions of B using methyl orange indicator. Tabulate your burette readings and calculate the volume of acid used.
The equation for the reaction is Na2CO3
+ 2HCL——————>2NaCl +H20 +CO2, from the result determine
(i)   Concentration of A in mol/dm3
(ii)  Concentration of B in mol/dm3
(iii) Molar mass of Na2CO3
(iv) Volume of CO2 liberated (HCl= 35.5g/mol)
Take the end point to be 21.10cm3

2. 25 mL of NaOH solution of unknown concentration was titrated with 3.0 M H2SO4 in the burette. The following data was obtained: Initial reading of burette = 0

Final reading of burette = 23.4 mL. What is the molarity of NaOH solution? What is the amount of NaoH in the titration solution?

Determine the number of ions in 3.M of H2SO4 ?.