SCIENTIFIC OBSERVATIONS AND STOIKIOMETRY
CHAPTER
1
PRELIMINARY
1.1 Background
If we talk about chemistry, surely we will remember
the atoms, the molecular elements, and the changes or reactions that occur
between them. Chemical elements can be found in both free and non-existent and
some artificial. The elements are usually denoted by letters which stands for
the element's name. These elements can also be formulated.
Chemical reactions can be found everywhere for
example that is not far from us, for example in our body there is a chemical
reaction, for example our body fluids consisting of chemicals in ions. In our
body there is also the process of digesting food with the help of enzymes and
combustion process.
In this experiment 1, it will be tested and
discussed on scientific observations and stoichiometry: KClO3 measurements.
Scientific observations are related to the scientific method. Scientific method
is a step or a way to get a truth from the observations made. The scientific
method uses three steps: scientific theory, hypothesis and experimentation. In
general the stages undertaken are finding problems or observations, collecting
data, submitting hypotheses, conducting experiments, drawing conclusions and
writing scientific reports. Stoichiometry learns about chemical calculations
that connect magnitudes or units of atoms that can be measured laboratoryally.
Stoichiometry studies about the atomic period, the number of particles, moles,
percent mass, empirical formulas and molecular formulas, and stoichiometric
applications in life. The chemical reaction of the dilam can be measured by the
chemical equation called the concept of mole. For example, calculate the amount
of CO2 emitted by 2 literbensin burned in a motor vehicle.
1.2 OBJECTIVES
1. Gain
experience in recording and explaining experimental observations.
2. Develop
skills in handling glass tools and transferring solid or liquid chemicals.
3. Familiarize
yourself with the safety procedures in laboratory work.
4. Determine
the KClO3 reaction coefficient coefficient.
5. Calculates
the molar volume of oxygen gas in STP state.
6. Calculates
the percentage of O2 in KClO3
CHAPTER
II
THEORETICAL
BASIS
Chemistry is a branch
of science that studies the material and its changes. Fundamentally, science is
scientific knowledge systematically compiled through a carefully designed
series of experiments, careful observations, to conclusions drawn with cendika.
This procedure, known as the scientific method, involves three steps, namely
the legal or scientific theory of hypotheses and experiments (Drs.Epinur, 2015:
17).
Chemistry is classified
as a science that specifically studies material changes, both chemical and
physical changes. Material change is a major study in chemistry, because
material change is a natural phenomenon that needs to be studied and understood
in order to be made. Changes to the favorable. Material change is always
accompanied by changes in energy in the form of heat (Yayan Sunarya, 2010: 2).
Chemistry is built by
two pillars of study that support each other, so that chemistry develops until
now and develops until the end of time. The two pillars are theoretical and
empirical studies. Both pillars of the study were used to develop chemistry
using systematic steps called the scientific method. In its simplest form, the
scientific method consists of the observation stage, searching for patterns
based on observation, theoretical formulation, theory testing and conclusion
(Yayan Sunarya, 2010: 3-4).
Stoichiometry is a study of the mass of a chemical
species in a chemical reaction quantitatively. Stoichiometry is based on 3
chemical laws, namely:
a. The
law of conservation of mass of substances before and after the reaction is the
same. (Lavoiser law)
b. Comparative
law remains: on a chemical compound the mass ratio of each constituent compound
is fixed. (Proust's law)
c. The
law of multiple comparisons: if two elements form a compound then the mass
ratio of each constituent of the compound is a simple number. (Djulia Onggo,
2013: 3)
Stoichiometry relates
to quantitative relationships between elements in a compound and between
substances in a reaction This term comes from the Greek language, namely
stoicheon and metrain. Stoicheon means element and metrain means measure. The
basis of all stoichiometric calculations is the knowledge of atomic mass
CHAPTER III
PRACTICAL METHOD
3.1 Tools and materials
Tools:
1. Florence flask
2. Copper metal
3. Pumpkin erlemenyer
4. 150ml cup glass
5. Filter paper
6. Glass watch
7. Passengers
8. Cup
Material :
1. Blue solution (10
grams glucose in 300 ml KOH 0.5 m and 10 ml 0.1 g methyl blue solution)
2. Concentrated nitric
acid
3. Sugar
4. 15 ml of
concentrated sulfuric acid
5. 40 ml of ethanol
6. Clean water
7. 3.9 ammonium sulfate
8. Zinc powder
9. Ammonium chloride
10. Calcium chloride
3.2 Work Procedures
Scientific observation
A. Demonstration by
assistant
a. The blue color
disappears
110g blue glucose
solution in 300 ml 0.5 ml KOH and 10 ml of methyl blue solution, Included in
Florence flask, threaded and shaken once with lid held by thumb, Repeated
experiment 2 to 3 times
b. Black foam
Granulated sugar Put
into a 150 ml cup of glass until half filled 15 ml of concentrated sulfuric
acid Added into a glass cup Stirred carefully with a glass stirrer
c. heat
40 ml of ethanol and
water Entered into 150 ml cup glass, saringiambi paper and soaked in alcohol
solution, Excess solvent squeezed and stretched on a watch glass, then burned
CHAPTER IV
RESULTS AND DISCUSSION
4.1 RESULTS AND
DISCUSSION
1. Scientific
observation
A. Demonstration by
assistant
1). The blue color is
gone
|
Observation
|
Hypothesis
|
|
Glucose
+ KOH + methyl blue if stirred continuously, the color of the solution will
change from dark blue to light blue then become clear (blue is gone)
|
The
blue color disappears from the reaction between glucose and KOH
|
4). Black foam
|
Observation
|
Hypothesis
|
|
Sugar
+ concentrated sulfuric acid after continuous homogeneous stirring of the
color into solid black but no foam
|
The
black color indicates the presence of carbon content
|
3). Heat
|
Observation
|
Hypothesis
|
|
Hypothesis
Ethanol + aquades are mixed homogeneously, then the paper is dipped into the
mixture
|
Then
the resulting fire was burned blue but the paper did not burn. Alcohol has
flammable properties. And water can not burn
|
1. Scientific Observations
a. Blue color disappears
In
this reaction the OH ion at KOH binds to H + derived from glucose. This
neutrality produces water so that water causes the color in the solution to
vanish. That's also because glucose is a neutral electrolyte in water, when
reacting with KOH which is a strong electrolyte can make the color birru to
disappear.
b. Black foam
The
ingredients used are sugar which is inserted into glass of cup 150 ml until
half filled then added 15 ml of concentrated sulfuric acid, then stirred with
caution. In this experiment not produced black foam, only black color is
visible and this experiment is declared failed. What causes this experiment to
fail is that the sugar is used too little and the sulfuric acid dosage is less
precise. Theoretically can be written: C12 H22 O12 + H2SO4 12C + H2SO4 + 11
H2O.
c. Heat
The
material used is 40 ml of ethanol which is incorporated into 60 ml water, then
dipped filter paper and placed in a watch and burned. At the time of being
burnt, blue flames and filter paper are not burned. This proves that yng burn
is ethanol, while the filter paper is not burned because it contains water. The
resulting blue color is the flame color of ethanol.
5.1 CONCLUSION
From experiments on scientific observation and
stoichiometry of the decomposition of KClO3 which has been done, it can be
concluded that:
1. Praktikan can gain experience in recording,
perform proper working procedures, explain experimental observations by using
scientific observations to propose hypotheses using scientific methods and
scientific experiments conducted.
2. In handling glass tools should be carefully,
because the glass material can easily break. Therefore, thick glass materials
such as test tubes of pyrex and in the experiment are used, when using a test
tube should be placed in a staple brace. In producing chemicals can be done
with caution. Solid chemicals must be dissolved in water first and if you want
to mix one solution with another solution, pour it bit by bit
