Learn about the conductometric titration of strong acid vs strong base through a laboratory experiment or practical.
Aim:
To determine the strength of strong acid using a strong base by conductometry.
Requirements:
Glasswares: Burette, burette stand, conical flask, volumetric pipette, beaker, volumetric flask, funnel, glass rod, and wash bottle, etc.
Chemicals: LR grade sodium hydroxide (NaOH), hydrochloric acid (HCl), potassium hydrogen phthalate (KHP), anhydrous sodium carbonate (Na2CO3), phenolphthalein indicator, and methyl red or methyl indicator, etc.
Apparatus: Digital/analytical balance, and ultrasonicator, conductometer, and magnetic stirrer.
Principle:
The principle of conductometric titration is based on the fact that one of the ions is replaced by the other during the titration, and these two ions usually differ in ionic conductivity, causing the conductivity of the solution to change during the titration.
HCl directly titrates with NaOH to determine its strength, in which sodium hydroxide is a strong base while hydrochloric acid is a strong acid.
Preparation of reagents and solutions:
Preparation of 1 M hydrochloric acid solution:
Take 85.00 ml of hydrochloric acid (HCl) using a pipette, dilute in 1000 ml of distilled water in a volumetric flask, and properly mixing it.
Preparation and standardization of sodium hydroxide:
Click here to get the procedure of preparation and standardization of sodium hydroxide (1M) solution.
Titration procedure:
- All glassware should be cleaned and dried according to standard laboratory procedures.
- Before filling the burette for the titration, rinse it with distilled water and then pre-rinse it with a portion of the titrant solution. Pre-rinsing is required to make sure that all solution in the burette is the desired solution, not a contaminated or diluted solution.
- Take the unknown stock solution of titrant in a clean and dry beaker then fill the burette using the funnel.
- Remove air bubbles from the burette and adjust the reading to zero.
- Switch ON the instrument and calibrate the conductivity meter with a standard solution. (Because potassium chloride (KCl) is soluble and stable, it is the most commonly used calibration solution for conductivity meters)
- Once it is calibrated, rinse the platinum electrode with distilled water.
- Take 50.00 ml of hydrochloric acid, pour it into a beaker.
- Properly place the beaker on a stirrer and immerse both the platinum electrodes and set the burette properly on the beaker.
- Note down the initial reading (conductance) of the sample i.e. millisiemens (mS) or micro-siemens (µS).
- Turn on the stirrer and add 01.00 ml standardized NaOH solution from the burette at a time, properly record the readings.
- Continue the titration process until the endpoint is reached.
- The actual endpoint of the titration is indicated by a sharp increase in the conductivity of the sample.
- Even after you've reached the endpoint, take a few more readings.
- Plot the graph between conductivity (mho) vs volume of NaOH and calculate the strength of hydrochloric acid (HCl).
Calculations:
M1V1= M2V2
M2 = V1 M1 / V2
Where,
M1 is the molarity of sodium hydroxide
V1 is the volume of sodium hydroxide
M2 is the molarity of hydrochloric acid
V2 is the volume of hydrochloric acid
Result:
The strength of hydrochloric acid was found to be___M.
Commonly asked quetions on conductimetric titrations are as follows.
What happens when a strong acid is titrated with a strong base?
In the titration of a strong acid-strong base, the acid and base will react to form a neutral solution. The hydronium (H+) and hydroxide (OH-) ions will react to form water at the reaction's equivalence point, resulting in a pH of 07.00.
What is the best indicator for strong acid-strong base titration?
Phenolphthalein indicator is the best indicator for strong acid-strong base titration.
Which is the example conductometric titration of a weak base with a strong acid?
The titration of hydrochloric acid (HCL) in the form of strong acid and ammonium hydroxide (NH4OH) as the weak base is an example of conductometric titration of a strong acid with a weak base.
