The use of plant extracts as indicators in teaching acid-base titrations: Case of Hibiscus sabdariffa (Zobo), Beta vulgaris (Beet root), Hibiscus rosa sinensis and Acalypha wilkesiana

Abstract

Acid-base titrations are the main part of volumetric analysis in the secondary school chemistry practical syllabus in Nigeria. Synthetic indicators are generally used in teaching students the procedure and skills required in acid-base titrations. However, some of these synthetic indicators are not readily available, some are toxic and there is a special procedure to be followed in preparing them for use as indicators. Hence there is need to consider the suitability of natural indicators which are more readily available, easy to prepare and ecofriendly compared. Therefore, this study aimed at investigating the suitability of Hibiscuss rosa sinensis, Acalipha wilkesiana, Hibiscus sabdariffa and Beta vulgaris L. extract as indicators in acid-base titration. The results showed that in strong-acid strong-base titration, all the plant extracts under study are suitable. All the plant extracts are fairly suitable for strong-acid and weak-base, except Beta vulgaris L. which is unsuitable for this titration. H. rosa sinensis is most suitable for weak-acid weak-base titrations similar to phenolphthalein, Acalipha wilkesiana is fairly suitable while H. sabdariffa and Beta vulgaris L. are unsuitable. For weak-acid strong-base titrations, all the plant extracts are fairly suitable especially H. sabdariffa. It was recommended that the use of these flower extracts as acid-base indicators should be incorporated in the teaching of acid-base titration especially in the secondary schools.