A questionnaire composed of two chemical equations has been administered to 203 second form scientific pupils from 15 Bunia schools in the Democratic Republic of the Congo in order to point out the errors they make in the equilibration of the redox reactions and identify the frequent errors. The obtained results, after the present study have revealed that the committed errors in the redox oxidation equilibration by these pupils are: the calculation of the stage oxidation, the oxidant identification and the reducer, the writing of redox couples, the half-equation redox writing, the reactionary area identification, the calculation of the least common multiple, the addition of the redox half-equation and the stoichiometric coefficient writing. By submitting these results to the Chi-Squared test, it has been found that the observed difference between the revealed error frequencies is very significant because Χ2cal = 327,40 ˃ Χ2tab 5% = 14,07. Thus, the most frequent errors are the oxidation numbers bad calculation (47, 78%), the confusion between the oxidant and the reducer (16, 26%) and the bad writing of the half-equation reduction oxidations (26, 11%). Teachers should, therefore exploit correctly the school books and the necessary procedures for the equilibrium of a redox reaction, but also find new methods to teach well the equilibration steps of an oxidation reaction and the reducer.

A written test has been administred to 226 pupils of the fourth form scientific, chemistry-biology option of 11 schools of Bunia town in DR Congo in order to evaluate the level of acquisition of total ionic reactions by the surveyed pupils. The obtained results at the end of these tests have shown that these pupils do not master correctly the notions of total ionic reactions taught to them (38,94 % of success). These pupils are very skillful in the explaination test (60,18 %) rather than in the execution test (13,72 %). In fact, they easily master the concepts to be memorized ; on the other hand, their failures concern the determination of the electronic transfer of ion, ionisation of molecules in the ionic reactions, the complete writing of a chemical equation and to the preparation of a compound considering the chart representing the characters of volatility and insolubility of a compound. The analysis of the variances of the average results of schools do not significantly differ to the threshold of the significance of 5 % (Fobs 0.05 = 0,81 < Ftab 0.05 = 1,87). This shows that the pupils of 4th form scientific, chemistry-biology option of Bunia town in RD Congo have the same level of mastering of the notions of the total ionic reactions.