lab 1
TRANSCRIPT
Name: Rhondene Wint
ID #: 24100032
Lab: Organic Chemistry I
Time: Mondays 5pm -8pm
Title: Separation of the components of a mixture.
Aim: To separate the individual components of mixture of sand, salt and naphthalene by using
separation techniques,
Abstract:
The title of the lab is the separation of the components of a mixture. The primary objective was
to separate a mixture of sand (silicon dioxide), salt (sodium chloride), and naphthalene so as to
arrive back the original weight. The original weight of this mixture was 2.02g. The techniques
involved were sublimation, filtration and evaporation. While carrying out separation techniques,
factors such as the solubility, melting point, boiling point and in some cases magnetism must be
considered. Sublimation is the process by which a solid is directly converted to the gaseous
phase. Filtration involves separating an insoluble solid from a liquid using a porous material.
Evaporation is the process of heating a mixture in order to remove the volatile liquid component
so as to leave the remaining solid component dry. The first step was to separate the naphthalene,
which is able to sublime at room temperature however heat was added to accelerate the process.
After it had deposited its mass was found to be 0.25g. The next steps included separating the
sand from salt. This was done by thoroughly mixing the salt-sand mixture in water until all the
salt had dissolved, and then mixture was filtered. The filter paper (of known weight) containing
the sand was placed in an oven to dry. The salt was then recovered by evaporation of the filtrate.
The masses of the sand and salt were 1.64g and 0.15g respectively. The percent purity of each
component was determined by the formula (mass of component/mass of mixture)*100. When the
percent purities were summed the result was 101.01%, which above the 100% mark. This is due
to the fact that the total weight of the components was 2.04g- greater than the original mass.
Therefore it was inferred that either the sand or salt had retained water.
Introduction:
A mixture is a combination of two or more substances that are not chemically united and do not
exist in fixed proportions to each other. Mixtures may exhibit a changing set of physical
properties; because substances in a mixture is physically combined their chemical properties are
not altered .There are two main categories of mixtures – homogeneous mixtures (alloys, colloids,
solutions), and heterogeneous mixtures. The main property which distinguishes heterogeneous
mixtures from homogeneous mixtures is particle size. A homogeneous mixture has the same
uniform appearance and composition throughout; many homogeneous mixtures are commonly
referred to as solutions. Homogeneous mixtures have only one phase, or have a uniform
appearance throughout, and any portion of the sample has the same properties and composition.
Each region of a sample is identical to all other regions of the sample, and individual
components will not settle out after standing. Types of homogeneous mixtures include colloids
and solutions. A colloid is a homogeneous solution with intermediate particle size between a
solution and a suspension. Colloid particles may be seen in a beam of light such as dust in air in
a "shaft" of sunlight (milk, fog, and jello are examples of colloids). A solution is mixture of two
or more substances in a single phase. At least two substances must be mixed in order to have a
solution. The substance in the smallest amount and the one that dissolves or disperses is called
the SOLUTE. The substance in the larger amount is called the SOLVENT. In most common
instances water is the solvent. The gases, liquids, or solids dissolved in water are the solutes.
Types of solutions include: liquid-liquid, solid – liquid, gas – liquid, solid-gas, gas – solid, solid-
solid, and gas- gas. A solution that contains a little solute in a given amount of solvent is dilute.
We called a solution contains a lot of solute in a given amount of solvent concentrated. A
saturated solution is a solution which has dissolved all the solute, at a given temperature. An
aqueous is to describe water when it is used as a solvent. A heterogeneous mixture on the other
hand is made of more than one phase and can be separated physically. They also do not have a
uniform composition throughout the mixture and its components are not soluble in each other.
Suspensions and emulsions are two special types of heterogeneous mixture. A suspension is a
mixture of solids and liquid in which the solids do not dissolve in the liquid solution. When a
suspension is allowed to stand for some time and left undisturbed, the solid particles settle at
bottom of the container. An example of suspension is sand in water and clay in water. An
emulsion is a special type of suspension where a mixture consists of two immiscible liquids (do
not mix together). When two such liquids are kept together they do not mix, no matter how much
you try to do so by shaking or stirring. They will eventually settle into two layers one above the
other when left undisturbed for considerable period of time. Examples of emulsions are kerosene
and water and a mixture of oil and water. Both suspensions and emulsions show the Tyndall
effect.
Separation techniques are done based on the properties of the individual substances of a mixture
and the nature of the mixture itself. Some factors which affect the type of separation technique
done are: boiling point, melting point, solubility, and magnetism. Filtration is a method which
is the most especially effective for separating suspensions by employing the use filter paper and
filter funnel. The solid remains in the filter paper is the residue, and the filtrate is the collected
liquid solution. Evaporation separates solids which do not decompose easily when heated in
solution. Crystallisation is a process of forming crystals. It is also a method for separating
dissolved solids from a solution. Sublimation separates a mixture of two solids in which one
sublimes, but the other does not. Simple distillation separates solid-liquid solution in order to
recover both the liquid solvent (distillate) and the solid. Fractional distillation separates a mixture
of miscible liquids with different boiling points. A separating funnel is used to separate an
emulsion. Magnetism separates magnetic substances from non magnetic ones. Chromatography
is used to separate a sample (or sample extract) being dissolved in a mobile phase (which may be
a gas, a liquid or a supercritical fluid. Other techniques also exist such as centrifugation,
decantation, etc..
The apparatus and materials used in this lab were filter funnel, filter paper, hot-plate, clamp and
stand, evaporation dish, beakers, stirring rod, analytic balance, oven, spatula, ice and water. The
filter funnel in conjunction with the filter paper was used to carry the filtration of sand from salt
solution. The clamp and stand was used to hold the funnel in place. Analytical balance was used
to determine the mass of substances. Beakers were uses to hold the mixture and other
compounds. Evaporating dish was used for separating the salt from the water. The spatula was
used to scrape off the deposited naphthalene, the stirring rod was used to dissolve the salt in the
water, and the hot-plate was used to apply heat. The ice was used to allow the naphthalene vapor
to deposit on the bottom of the evaporating dish, and water was used to create a salt solution –
sand suspension. The reagents or primary chemicals are: sand, salt and naphthalene. Sand is
mainly composed of silicon dioxide (SiO2). Silicon dioxide or silica is the most abundant
mineral in the Earth's crust, and it is found across the world in various forms. Crystalline silicon
dioxide (in several forms: quartz, cristobalite, tridymite) is an important constituent of a great
many minerals and gemstones, both in pure form and mixed with related oxides.
In the vast majority of silicates, the Si atom shows tetrahedral coordination, with 4 oxygen
atoms surrounding a central Si atom thus the bond angles around O-Si-O are essentially the
tetrahedral angle, 109.5 degrees. SiO2 has a number of distinct crystalline forms (polymorphs) in
addition to amorphous forms. With the exception of stishovite and fibrous silica, all of the
crystalline forms involve tetrahedral SiO4 units linked together by shared vertices in different
arrangements. Silicon-oxygen bond lengths vary between the different crystal forms. Silicon
dioxide is formed when silicon is exposed to oxygen (or air). A very shallow layer of native
oxide is formed on the surface when silicon is exposed to air under ambient conditions.
Alternative methods used to deposit a layer of SiO2 include:
Low temperature oxidation (400–450 °C) of silane
SiH4 + 2 O2 → SiO2 + 2 H2O.
Decomposition of tetraethyl orthosilicate (TEOS) at 680–730 °C
Si(OC2H5)4 → SiO2 + 2 H2O + 4 C2H4.
Plasma enhanced chemical vapor deposition using TEOS at about 400 °C
Si(OC2H5)4 + 12 O2 → SiO2 + 10 H2O + 8 CO2.
Sand or silicon dioxide is insoluble in water and has a high melting point of 1600-1725 °C and
boiling point of 2230 °C. Its average density is 2.648gcm-3.
Strong ionic bonding unites the elements sodium and chloride to make the chemical compound
sodium chloride. Sodium chloride (NaCl) or common salt is an ionic crystal consisting of equal
numbers of sodium and chlorine atoms and is an essential component in the human diet, being
found in blood sweat and tears. Sodium chloride has a cubic crystalline structure, Is clear when
pure, although may also appear white, grey or brownish, depending upon purity, soluble in water,
slightly soluble in other liquids, odorless, has a characteristic taste, molten or aqueous sodium
chloride is an electrical conductor. Each ion is surrounded by six ions of the other kind;
Naphthalene (C8H10) is a white crystalline solid with a characteristic odor. As an aromatic
hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings ((In organic
chemistry, rings are fused if they share two or more atoms . Most naphthalene is derived from
coal tar. Naphthalene is mainly used as a precursor to other chemicals. The single largest use of
naphthalene is the industrial production of phthalic anhydride. A characteristic property of
- Na+
- Cl-
naphthalene is that sublimes at room temperature and is insoluble in water.
Method:
Procedures done as outlined in Laboratory Experiments for General , Organic & Biochemistry
Fifth Edition. pp 40 – 43, Experiment 4.
Discussion:
Results:
1. Weight of Beaker1
2. Weight of Beaker1 + mixture
3. Weight of Mixture only ( 2- 1)
4. Weight of Beaker1 + mixture – naphthalene
5. Weight of Naphthalene (2-4)
6. Weight of Beaker2
7. Weight of Beaker2 + salt
8. Weight of salt
9. Weight of Beaker3
10. Weight of Beaker3 + sand + filter paper
11. Weight of sand (10-9 -12)
12. Weight of filter paper
b. Percentage of each component in the mixture:
Salt: (0.15g/2.02g) * 100 = 7.43%
Sand: (1.64g/2.02g) * 100 = 81.19%
Naphthalene: (0.25/2.02g) * 100 = 12.38%
Total mass = 1.64g + 0.25g + 0.15g = 2.04g
The mixture used in the lab was an example of a heterogeneous mixture in which the
components were not dissolved in each other, and its composition was not uniformed.
Naphthalene was separated first by sublimation because it had to the ability to sublime, and the
other components could not. The reason the ice was placed in the evaporating dish, which
covered the beaker during sublimation, was because the heat energy that released from the
melting of the ice was absorbed by the naphthalene vapor causing the naphthalene to deposit or
condense on the dish’s bottom so that it could be collected. Before the sand could be separated
from the salt, water was needed to be added so that the salt could dissolve in leaving the
insoluble sand behind. Water dissolves many substances by surrounding charged particles and
"pulling" them into solution. When water was added to salt, the partial charges on the water
molecule are attracted to the Na+ and Cl- ions. The water molecules work their way into the
crystal structure and between the individual ions, surrounding them and slowly dissolving the
salt. The water molecules will actually line up differently depending on which ions are being
pulled into solution. The negative oxygen ends of water molecules will surround the positive
sodium ions; the positive hydrogen ends will surround the negative chlorine ions. The last step
was to recover the salt by evaporation because salt (NaCl) has a high melting point/ boiling point
due to its strong ionic bonds therefore it does not decompose at the temperature at which water
boils.
The results are self explanatory as to how the mass of each substance was determined. However
it is evident that errors occurred in the experiment as the total mass of the components is greater
than the original mass of 2.02g. This could be as a result of the either the sand not drying
properly and /or the salt retaining some water. Another possible source of error is that some
naphthalene vapor may have escaped from the aperture of the beaker because the beaker was not
fully covered by the evaporating dish. It can be concluded that the individual components of a
mixture either heterogeneous or homogeneous can be isolated by employing correct separation
techniques.
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