The
flame test is a classical analytical method that is often used to
teach students how to identify specific metals. However, some universities
in developing countries have difficulties acquiring the sophisticated
instrumentation needed to demonstrate how to identify and quantify
metals. In this context, a method was developed based on the flame
test to quantify sodium in coconut water and seawater using recorded
videos of a flame during the experiment and subsequent image treatments
with an R statistics platform. This experiment provided undergraduate
students an opportunity to study important topics such as atomic theory,
emission spectroscopy, quantitative analysis, and image processing.
Finally, students measured the sodium content in seawater collected
from a region of the Rio Grande do Norte coast, an important region
for manufacturing salt. They obtained sodium concentrations that ranged
from 11.2 to 12.2 g dm–3 and calibration curves
that presented good linearity (R
2 >
0.91). The sodium content of coconut water determined was 48 ±
4 mg dm–3. The results demonstrate an interesting
and simple method that can easily be applied in experimental Analytical
Chemistry courses, and this experiment would also be appropriate for
pre-college students.
A chemometrics course is offered to students in their
fifth semester of the chemistry undergraduate program that includes
an in-depth project. Students carry out the project over five weeks
(three 8-h sessions per week) and conduct it in parallel to other
courses or other practical work. The students conduct a literature
search, carry out laboratory work, and write a technical report on
a research subject of self-choice. In the project described here,
the students worked on experimental design, using near-infrared spectroscopy
and multivariate calibration, to develop methods to predict the properties
of biodiesel and diesel blends. In addition to dealing with the chemometric
tasks, the students synthesized the biodiesel sample and understood
the importance as a renewable energy source.
Stoichiometry has always been a puzzling subject. This may be partially due to the way it is introduced to students, with stoichiometric coefficients usually provided in the reaction. If the stoichiometric coefficients are not given, students find it very difficult to solve problems. This article describes a simple 4-h laboratory experiment for the determination of aluminum content in commercial samples through the stoichometric relationship between aluminum and released hydrogen gas. The experiment was performed by highschool students at an advanced preparation course for the Chemistry Olympiad. The aluminum content in foil samples was determined by measuring the amount of formed hydrogen gas through mass balance of the reaction system. The experiment is appropriate for high-school chemistry or a first-semester general chemistry course."We may lay it down as an incontestable axiom, that, in all operations of art and nature, nothing is created; an equal quantity of matter exists both before and after the experiment; the quality and quantity of elements remain precisely the same; and nothing takes place beyond changes and modifications in the combination of these elements." 1
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