A Dramatic Hands-on Activity of Limiting Reagent Concept from the
Vinegar and Sodium Bicarbonate Reaction
Romklao Artdej
This hands-on activity is a part of the National Science and Technology Fair
2008, at the BITEC convention center, Bangkok. Many students, teachers, and
interested persons participated in this hands-on activity.
The activity is a newly designed chemistry laboratory for secondary students.
It aims at showing the relationship between science and daily life. In this activity, the
participants were actively involved in the exploring quantitative relationship between
household chemicals found in daily life, e.g. vinegar (CH3COOH) and baking soda
(NaHCO3). The participants conducted the experiment by measuring the volume of
carbon dioxide gas produced from the reaction between vinegar and baking soda.
The reaction can be described as follows:
CH3COOH (aq) + NaHCO3 (s)
CH3CO ONa (aq) + H2CO3 (aq)
…(1)
H2CO3 (aq)
H2O (l) + CO2 (g)
…(2)
CH3COOH (aq) + NaHCO3 (s)
CH3COONa (aq) + H2O (l) + CO2 (g) …(3)
From the overall reaction, carbon dioxide gas is produced and its volume can be
measured by using a principle of liquid displacement by gas. The participants
discover the concept of limiting reactant via a series of experiments where the amount
of vinegar is fixed and the amount of NaHCO3 is gradually increased. The volume of
CO2 generated from the reaction varies corresponding to the amount of NaHCO3 until
it reaches the point where the CO2 volume remains constant no matter how much
NaHCO3 is used. The result clearly leads to the conclusion that before the equivalence
point, NaHCO3 is the limiting reagent and vinegar becomes the limiting reagent
afterwards.
This activity relates to the standard science 3.2 underlying the sub-strand 3
which students should be able to understand the principles and nature of change of
states of matters, formation of solution, chemical reaction, master investigative
processes and possess a scientific mind, communicate knowledge acquired and apply
it positively. This hands-on activity also promotes positive attitude towards science
literacy.