Universal Journal of Educational Research 4(5): 1158-1162, 2016 http://www.hrpub.

org
DOI: 10.13189/ujer.2016.040527

Wither the Concepts of Mole and Concentration:

Conceptual Confusion in Applying M1V1 = M2V2
Sheau Huey Chong

Faculty of Applied Sciences and Computing, Tunku Abdul Rahman University College, Malaysia

Copyright©2016 by authors, all rights reserved. Authors agree that this article remains permanently open access under the
terms of the Creative Commons Attribution License 4.0 International License

Abstract Concentration of solutions problems are among the abstract nature of the subject [6]. Besides, chemistry
the most important and at the same time one of the most educators and chemistry textbooks often present chemistry
challenging topics in chemistry. The aim of this study was to knowledge over at least three levels of representation (i.e.
determine the sources of the difficulty that students often macroscopic, submicroscopic, and symbolic) for which
face when performing calculations related to concentration. Johnstone [7] claimed that this offered too much complexity
The study involved 153 tertiary college students (food for the beginning chemistry students. For example, for an
science, chemistry and biology majors) who have learned the aqueous solution of sodium chloride, the macroscopic
concepts of mole and concentration of solutions prior to the representations refer to what can be seen. The
study. Students' written working steps in answering two submiscroscopic illustrates a particle model with invisible
concentration questions in the semester summative particles dispersed in all directions of the solution. The
examination were analyzed. The results showed that 52 % of symbolic shows the chemical formula, NaCl. Nyachwaya et
students answered Question 1 correctly whereas only 28 % al [8] reported that competence in algorithmic problem
of students solved Question 2 successfully with a clear solving did not translate to competence in conceptual
display of conceptual understanding. Analysis of students' understanding. If this fundamental ‘levels of representation’
answers led to the identification of common errors, in is not understood, it may inhibit learning of more advanced
conceptual understanding of the topics. It was revealed that topics such as solution concentration. The mole concept
one contributing factor to the poor success rate in solving (amount of substance) is a concept that connects the
problems related to the concentration was the superficial macro-world with the micro-world. Mastery of this concept
understanding of the mole concept. Mastery of the mole is of utmost importance as it equips students to learn the
concept is foundational to understanding concentration of solution concentration topic with ease. However, many
solutions. Difficulties with the former may inhibit learning students treat the mole concept and the concentration of
of the latter. However, the results of this study implied that solutions as separate entities and their knowledge in these
inappropriate application of the formula M1V1 = M2V2 was areas are always compartmentalized. This makes the process
the main problem students faced in solving the questions. of learning and teaching challenging.
Specifically, students faced difficulties understanding the Numerous studies exist in chemistry education literature
use and the meaning of M1V1 = M2V2. A lack of conceptual that deals with students' learning difficulties, alternative
understanding of the mole concept appeared to lead students conceptions and problem solving strategies in the mole
to rely on the use of memorized formulae and steps to solve concept. For example, Ault [1] claimed that teaching of
the questions. Implications for assessment, research and stoichiometry has focused on the symbolic level of
instruction are also included. representation relying heavily on algorithms which does not
promote conceptual understanding. Staver et al [9] stated
Keywords Molarity, M (mol dm-3) x Volume of a that students have the following two deficiencies: (a)
Solution, V (dm3) = Amount of Substance (Mole as a Unit) incapacity to navigate meaning between the macro level and
the sub-micro level when solving problems; and (b)
insufficient understanding of the concepts and rote use of
algorithms and rules. Furio et al [5] found that the
1. Introduction conventional instruction of several chemistry courses in
secondary education does not result in the students relating
Stoichiometry problem solving is an area which poses a the idea of "amount of substance" with counting particles.
great challenge to students in chemistry learning. The Instead, they identified the "amount of substance" with mass
difficulties may due to the capabilities of human learning and and occasionally, with volume.
 Universal Journal of Educational Research 4(5): 1158-1162, 2016 1159

Meanwhile, Duncan et al [4] reported that students faced Table 1. Number of students according to programmes.
difficulties when the stoichiometric proportion in a reaction Programme No of students
was not 1:1. This led to another challenge where students Bachelor of Science (Hons) in Food Science
deal with solutions, because they did not consider that in 15
(first year)
diluting the aqueous solution of a substance, the volume of Diploma in Food Science (second year) 32
the solution changes. Research done by Devetak, et al [3]
Diploma in Food Science (first year) 56
highlighted difficulties faced by students in solving
Diploma in Science (Chemistry and Biology)
problems related to the concentration of solutions. A study (first year)
50
carried out by de Berg [2] revealed that first-year university Total: 153
chemistry students performed better when the problems of
sugar concentration in aqueous solutions were presented in Students from all programmes have learned the mole
verbal mode than in visual submicroscopic form. This shows concept and the concentration of solutions in the prior to the
that students probably are able to solve chemistry problems study. In this study, students' working steps in solving two
using memorized algorithms without conceptual concentration questions as shown in Table 2 in the semester
understanding. summative examination were analyzed. In the present phase
Previous studies have shown how difficult the topic of of this study, quantitative analysis was intended to gauge the
solutions proves to be across all levels of education. While prevalence of certain thought patterns and not to make
various studies have been carried out regarding students' generalization of the findings. All answers obtained were
conceptions and understanding of the mole concept and the examined and categorized by the same researcher and
concentration of solutions, there is a lack of explicit reviewed by two senior lecturers to ensure consistency.
investigation linking both concepts. Formula M1V1 = M2V2,
which combines both the mole concept and the concentration Table 2. Questions used in the study
of solutions is commonly used in chemistry calculations. Question 1:
Factors such as conceptual understanding and problem What is the resulting concentration when 3.5 L of 6.0 mol dm-3 HNO3
solving skills contribute to students' performance in is added to 2.5 L of 1.5 mol dm-3 HNO3? (Assume the final volume to
calculating problems related to the concentration of solutions. be exact 6.0 L)
It is an observation of the author that current college students Question 2:
display an inadequate understanding of the mole concept and Amines, RNH2, which is commonly found in bananas, grapes and
concentration which always leads to the inappropriate use of lemonsreact with picric acid to form amine picrates, which absorb
the formula. As such, the aim of this research was to examine strongly at 359 nm (molar absorptivity = 1.25 x 104 cm-1 mol-1 L). An
college students' written calculations (working steps) when unknown amine (0.1155 g) is dissolved in water and diluted to 100
mL. A 1-mL aliquot of this is diluted to 250 mL for measurement. If
trying to solve problems related to the concentration of
this final solution exhibits an absorbance of 0.454 at 359 nm using
solutions. a 1.00-cm cell, what is the formula weight of the amine?

2. Method
3. Results
This study is part of a larger research project in which the
author plans to develop and implement strategies in teaching 52 % of students answered Question 1 correctly whereas
the concentration of solutions to enhance students' only 28 % of students solved Question 2 successfully with a
understanding. 153 students (18-19 years old) from a private clear display of conceptual understanding. Examples of
college university in Malaysia participated in the study. The students' answers are shown on Figure 1 and Figure 2. The
number of students according to the various programmes distribution of the percentage of errors of participants is
offered at the institution is shown in Table 1. summarized in Table 3.
1160 Wither the Concepts of Mole and Concentration: Conceptual Confusion in Applying M1V1 = M2V2

Figure 1. Example of correct answer with clear display of understanding (Question 1).

Figure 2. Example of correct answer with clear display of understanding (Question 2).

Table 3. Distribution of the Percentage of Alternative Conceptions of Participants.

Alternative Conceptions in Question Alternative Conceptions (Question 1) Alternative Conceptions (Question 2)

Inappropriate substitution (due to
conceptual errors) to 42.4 % 57.4 %
M1V1 = M2V2
Mathematical error - 2.1 %
Did not attempt question 5.6 % 10.6 %
Applied wrong formula - 2.1 %
 Universal Journal of Educational Research 4(5): 1158-1162, 2016 1161

Figure 3. Example of an inappropriate substitution to M1V1 = M2V2 (Question 1).

Figure 4. Example of an inappropriate substitution to M1V1 = M2V2 (Question 2).

4. Discussion and Conclusion

From the analysis, the main conceptual error faced by the
students was lack of understanding of M1V1 = M2V2. The REFERENCES
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