A.
EXPERIMENT TITLE : Hydrogen & Oxygen
B. EXPERIMENT POURPOSE :
1. Knowing how to make hydrogen gas.
2. Knowing the properties of hydrogen gas and its compounds.
3. Identifying hydrogen gas and its compounds
C. BASIC THEORY
1. Hydrogen
Hydrogen has the simplest atomic structure of all the elements, and
consists of a nucleus containing one proton with a charge +1 and 1 orbital
electron. The electronic structure may be written as 1s1.
Hydrogen is the most abundant element in the universe. Some
estimates are that 92% of the universe is made up of hydrogen, and 7% of
helium, leaving only 1% for all of the other elements. However, the
abundance of H2 in the earth atmosphere is very small. This is because the
earth’s gravitational field is too small to hold so light an element, though
some H2 is found in volcano gases. In contrast, hydrogen is the tenth most
abundant element in earths crust ( 1520 ppm or 0,152% by weight). Its also
occurs in vast abundant, particularly water, living matter, organic
compounds, fossil fuel ammonia and acid.
Properties
Hydrogen’s unique properties distinguish it from all other elements in
the periodic table. It is often placed at the head of Group 1 because like the
alkali metals it has only one electron in its valence shell. That position,
however, does not truly reflect the chemical or physical properties of the
element. In particular, its ionization energy is far higher than the other
Group 1 elements, so hydrogen is not a metal, although it is predicted to
exist naturally in a metallic state where extreme pressures exist, such as the
core of Jupiter. In some versions of the periodic table hydrogen is placed at
the head of Group 17 because, like the halogens, it requires only one
electron to complete its valence shell. But the electron affinity of hydrogen
is far lower than any of the elements of Group 17 and the discrete hydride
ion, H−, is encountered only in certain compounds. To reflect its unique
characteristics, we place H in its own special position at the head of the
entire table. Because H2 has so few electrons, the intermolecular forces
between H2 molecules are weak, and at 1 atm the gas condenses to a liquid
only when cooled to 20 K. If an electric discharge is passed through H 2 gas
at low pressure, the molecules dissociate, ionize, and recombine, forming a
plasma containing, in addition to H2, spectroscopically observable amounts
of H, H+, H2+, and H3+. The H2 molecule has a high bond enthalpy (436 kJ
mol −1) and a short bond length (74 pm). The high bond strength results in
H2 being quite an inert molecule, and reactions of H2 do not occur readily
unless a special activation pathway has been provided. In the gas phase it is
much more difficult to dissociate H2 heterolytically than homolytically,
because the former incurs a large additional energy cost to separate the
opposite charges.
Preparation
In the laboratory, H2 is easily produced by the reactions of electropositive
elements with aqueous acid or alkali, or by hydrolysis of saline hydrides. It is also
produced by electrolysis.
There are many straightforward procedures for preparing small quantities of pure
H2.
reaction of Zn with mineral acids in the room temperature:
Zn (s) + 2H3O+ (aq) → Zn2+ (aq) + H2 (g) + 2H2O (l)
2. Oxygen
D. TOOLS AND MATERIALS
a. Tools
1. Crucible 1 piece
2. Wooden Tongs 1 piece
3. Bunsen Burner 1 piece
4. Porcelain Spoon 1 piece
5. Graduated Cylinder 100 mL 1 piece
6. Dropper Pipette 5 pieces
7. Test tube 5 pieces
8. Rubber Cover 1 piece
9. Statives and clamps 1 & 1 piece
10. Test tube pipe side 1 piece
b. Materials
1. Calcium metal
2. Magnesium powder
3. Zink powder
4. H2O2 3% solution
5. KI 0,1 M
6. H2SO4 0,1 M
7. Barium Peroxide
8. Glass cotton
9. Starch solution
10. PP indicator
11. HCl solution 4 M
E. LANES WORK
1. Experiment 1
A few pieces of calcium
metal
Inserted into a poselein cup
Added some aquades
Observed
Tets the solution using
lithimus paper
Red lithimus paper become
blue
Blue lithimus paper still blue
2. Experiment 2
A little spoon of Mg powder
Inserted into a poselein cup
Added some aquades
Heated in the bunsen burner
Tets the solution using PP
indicator
Color change
3. Experiment 3
Test tube
Successively put a slightly wet glass cotton,
dry glass cotton, then about 0.02 grams of
zinc powder, and finally dry cotton.
Cover the test tube with a rubber cap / cork
with a hole in the middle.
Hold the tube with wooden tongs
horizontally and then heat the section
containing the zinc over a bunsen flame, and
occasionally on the wet glass cotton.
Test the exiting gas with a flame
Flame
4. Experimnet 4
Side pipe test tube
Filled with some zinc metal
Connected with the hose that is connected to
the measuring cup holder that is placed
upside down in the water
Add enough 4 M hydrochloric acid solution
for the reaction to occur
Observation result
Flame tested
Cover with a rubber cover
Gas collected in the graduated cylinder
5. Experiment 5
1 mL KI + starch
Inserted into a tets tube
Added some drops of H2O2
3%
Observed
Observation result
1. Determine the amino acid component
F. EXPERIMENT RESULT
G. EXPLANATION
H. CONCLUSION
I. References
J. QUESTIONS ANSWERS
1. What are the advantages and disadvantages in the paper chromatography
separation method?
Answer:
a. Advantage:
1)In paper chromatography the equipment used does not need
complicated tools. Good results can be obtained with very simple
equipment and materials.
2)Separate compounds can be detected on paper and can be
immediately identified directly
3)The cost required is relatively cheaper when compared with
other separation techniques.
4)Preparative paper chromatography requires a larger paper than
for analysis. The advantage is that the load arm of the Rf number
becomes large so that the measurement of Rf is a valuable
parameter in exposing new compounds.
b. Disadvantage:
1)Cannot conduct quantitative analysis on sample components,
only limited to qualitative analysis.
2)The time is longer than other adsorbents, but shorter than TLC.
3)Cannot use H2SO4 reagent because cellulose will decompose.
2. Is the chromatographic method can be used for quantitative analysis?
Answer :
The paper chromatography method can be used both to carry out
quantitative and qualitative analyzes. Quantitative analysis is performed
based on the comparison of Rf of the sample substance with the Rf
value of the standard substance. In order for a quantitative analysis to
work well the following things must be considered:
1)The trial conditions must be the same, because the price of Rf
depends on these conditions
2)Must be tried with various solvents
3)The presence of stains on the chromatogram does not mean the
presence of a single substance in the sample
Whereas the qualitative analysis was carried out by identifying the
amino acid component of the sample against an amino acid solution that
had been known previously based on the value of Rf.
3. What are the factors that affect the Rf value?
Answer :
1) Solvent. This is due to the importance of the partition
coefficient, so very small changes in the composition of the
solvent can cause changes in the price of Rf.
2) The presence of other ions, for example the presence of
chloride in the separation carried out with nitrate solutions
3) Properties of the mixture. Various compounds partition
between the same volumes of fixed and mobile phases. The
nature of the mixture almost always affects the characteristics
of the solubility of one to another to also affect the price of Rf
4) Paper. The main effect of paper on the price of Rf arises from
changes in ions and uptake, which is different for different
types of paper. Paper affects the speed of the flow and affects
the balance of the partition.
5) Temperature. Changes in temperature change the partition
coefficient and flow speed.
6) Size of the vessel. The volume of the vessel affects the
homogeneity of the atmosphere, thereby affecting the rate of
evaporation of the solvent components of the paper. If a large
vessel is used, there is a tendency to propagate for longer
periods, such as changes in the composition of the solvent
along the paper, then the partition coefficient will change too.
Two factors namely evaporation and composition affect the
price of Rf.
7) Quality of adsorbents
8) Layer thickness. The thicker the Rf layer the smaller
9) Saturation of room chromatography (chamber
chromatography).
K. ATTACHMENT
1. Calculation
Calculating Rf value of solutions
Solution A (Tyrosine) :
Solution B (Lysine) :
Solution C (Alanine) :
Solution D (sample) :
