Before we begin, let’s see some of the apparatus you will be using during the chemistry practical exam.
Chemistry practical can be broadly divided into two, namely;
1 QUANTITATIVE ANALYSIS
2 QUALITATIVE ANALYSIS.
1 Quantitative analysis deals with determination of the amount or percentage of one or more constituent of a sample.
For the sake of WAEC, I will only touch the volumetric analysis (part of quantitative analysis) that is subdivided into four;
i Acid-base titration
ii Redox titration
iii complexometric titration
Iv precpitratory titration
i ACID-BASE TIRATION: is the technique employed to determine the amount of acid required to neutralize completely a given amount of base and vice-versa.
There are varieties of acid and base as shown below.
During the course of acid base titration you will need an indicator such as methyl orange, phenolphthalein, litmus paper etc. they tell you the end point of the titration.
The choice of suitable indicator depend on the strength of acid to that of base, it is analyzed below.
After the titration you will be asked to calculate molar mass, mole, mass, molarity etc. the formulas for these entity are shown below.
ii REDOX TITRATION: is a technique employed to determine the amount of reducing agent required to reduce completely a given amount of an oxidizing agent and vice-versa.
Oxidizing agent include potassium permanganate, potassium iodate iodine molecule etc. while
Reducing agent include potassium iodide, ethanedioic acid(oxalic acid), iron(ii) salt etc.
The below picture illustrate how to recognize a redox reaction.
Some of the calculation aspect of Redox titration is similar to acid base titration.
2 Qualitative analysis deals with the determination of the nature or type of chemical constituent present in a sample, it is further divided into two
i Inorganic qualitative analysis
ii Organic qualitative analysis
i INORGANIC QUALITATIVE ANALYSIS: these involved determination of
Cation: Ca, Zn, Al, Pb, Cu, Fe, NH4, K, Na.
Anion: CO3,HCO3, S, SO3, SO4, NO2, NO3, Cl, Br and I.
Gases : H2,O2, CO2, HCL, HBR, HI, Cl2, Br2, I2 and NH3.
Below table illustrate how these entity interact with reagents
ii ORGANIC QUALITATIVE ANALYSIS: these involve determination of organic functional group.
These functional group are shown in the chart below.
Some of the test for each functional group is analyzed below.
Note; Acidic substance (whether gas, or ion) changes blue litmus paper red while
Basic compound changes red litmus paper to blue.
Some of the ways you can write your precautions during titration analysis are:
1 I ensure that the apparatus were clean thoroughly before starting the experiment.
2 I ensure that the reagent were not contaminated
3 I remove the funnel on my burrete before taken any reading.
4 I ensure that the burrete was not slanted while taken my reading.
Some of the ways you can write your error during titration analysis are:
1 error due to parallax while taking reading from the burrete
2 error due to blowing of the pippete to force out the base.
3 error due contaminated reagent.
VIDEO PRACTICALS / TUTORIALS
These tips are invaluable in any chemistry practical exam; i hope you will find it handy.
Wish you best of luck in your exam.