Separating Mixtures Back Into Their Components | Experiment

Abstract

To separate these mixtures it was appropriate to understand the physical and chemical structures of all the substances situated within the mixture. After separating these mixtures based on their physical and chemical properties; it was then appropriate to compare their experimental masses compared to their actual masses. Once separating these mixtures and comparing their masses it was important to record any discrepancies which may have been observed throughout the experiment.

Background Information

The mixture was composed of the following substances;

• 5.5g sand
• 2.4g iron fillings
• 25ml methylated spirits
• 13g of NaCl
• 0.6 g of sodium sulfhate
• 13ml of hexane

The aim of this experiment was to separate a mixture back into its original components based on the mixtures physical and chemical components.

A mixture is when two or more substances are combined by forceful means, such as pouring substances into a container. The molecules of the combined substances then mix with the others to create the forms of solutions, suspensions and colloids. These mixtures can be classified as homogenous or heterogeneous solutions. A heterogeneous mixture contains unevenly distributed liquids, gases and particles. The sand, iron, and hexane are all immiscible substances when mixed in the mixture, therefore many unevenly distributed particles and liquids are present in the mixture, thus categorizing the mixture as a heterogeneous.

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Mixtures usually do not consist of chemical bonding between the substances, thus allowing the mixture to be separated using simple methods of filtration. As the mixture contains sand, iron, hexane and methylated spirits basic filtration can be applied based on each substances chemical and physical properties. However as NaCl and Na2S04 do undergo chemical reactions with the water present in the mixture; this creates a barrier for any type of filtration. It is therefore appropriate to analyze the chemical and physical properties of each NaCl and Na2SO4, and find an appropriate method to extract both miscible substances from the mixture.

Therefore it is applicable to note that substances are separated based on their chemical and physical properties. Therefore analyzing the physical and chemical properties of each component situated in the mixture, appropriate separation techniques can be identified.

The most obvious separable substance situated in the mixture is Hexane. Hexane is oil, used for many necessities of life, such as cooking. As seen in figure 1, hexane has the chemical formula C6 H14 and it only contains hydrogen and carbon atoms, thus putting the solvent into the category of an alkane (hydrocarbon). Hexane’s chemical structure is dependent on its alkane properties; its hydrogen’s are exclusively linked by single bonds to carbon, this is also known as a covalent molecule. As the electrons are being shared this creates similar charges for the hydrogen’s and carbon atoms. As both atoms electrons have similar negative charges they repel each-other and create a non-polar substance. As non-polar substances are immiscible in water, hexane will not mix in water as it’s a non-polar molecule. Instead of mixing in water, hexane with a light density of 0.654g/ml will sit on top of the water as water has a heavier density of approximately .995g/ml.

In contrast to hexane, water is a polar molecule. The two oxygen’s bound to the one hydrogen create a ‘V’ shape with the hydrogen atoms. As seen in figure 2 it is noticeable that when hydrogen atoms bond with oxygen, the hydrogen releases one of their electrons to form a covalent bond. Due to hydrogen’s electrons being attracted to the positive electron oxygen, the two hydrogen’s become slightly positively charged, and the oxygen then becomes negatively charged. (www.ozh2o.com, 2003). The dissociation of the positive and negative charges produces a polar molecule.

Due to the above mentioned physical and chemical properties of hexane and water, the most efficient way of separating hexane from the mixture, will be the use of decanting. And also using a separation funnel.

Decanting is the process of carefully pouring a lower density liquid off the top of another, such as hexane and water. It is poured into another beaker and then separated again using the separation funnel.

A separation funnel is used to slowly and carefully drop by drop separate the heavier in density substance (water).

Another substance that is present in the mixture that is also miscible in water is sand. Sand also known as silicon dioxide has a chemical formulae of Si02 and has a tetrahedral chemical structure, as seen in figure 3. Figure 3 clearly shows the four oxygen’s surrounding the central atom Si which creates a triangular shaped structure; hence the reason silicon dioxide can be classified as a tetrahedral crystal. Out of all the silica crystallines, on average only two out of the four oxygen’s of the Si04 are shared with others, giving the formula Si02 (book reference). Due to sand sharing pairs of electrons between its atom it consists of having an extensive covalent chemical bond. Its extensive covalent chemical bonding creates a strong bonding with the elements oxygen and Si, thus meaning the chemical formula Si02 is a strong element. As sand has a hard quartz figure it is insoluble with water, therefore separating sand from the mixture filtration can be used as it separates the liquids from the hard solutions. Another solution that has a hard like figure and is insoluble to water that is in the mixture is iron fillings.

Iron fillings are composed of iron or Fe. Iron fillings are a type of ferromagnetic material which can be easily attracted to a magnet. The electrons orbiting the iron atom resemble a current, thus this results in a small magnetism to each individual electron; this can be amplified by the spinning of the electrons. This then means the tiny pieces of iron can transform to a tiny bar magnetic when a magnetic field is in area of them, thus irons opposite ends attract to the opposite ends of a magnet. For example the north end of iron would be attracted to the south end of the magnet. As iron is also a substance that is insoluble in water the method filtration will be most effective to separate the iron from the mixture.

As iron is already classified as a ferromagnetic metal, this means its domain already consist of a high degree of magnetization. However as seen in figure 4, when coming into contact with a magnetic field, the domain become randomly orientated. Also when iron comes into contact with a more modest magnetic field the domain can become aligned in the direction of the force.

As both sand and iron fillings are insoluble in water, they will sink to the bottom of the mixture not having a chemical reaction with any other substances. This sediment at the bottom of the mixture can be separated first using filtration as the sand and iron will be trapped in the funnel paper. However to separate the sand from the iron, using a magnet will be appropriate as irons domain will be attracted to the opposite end of the magnet, as seen earlier in figure 4.

As seen in figure 5 filtration is the use of a funnel, funnel paper and a beaker. The beaker is used to catch the mixtures liquids and the funnel paper used to stop and absorb any fine sediment, in the case of the experiment iron and sand. Once the mixture is poured through the funnel paper the sand and iron will be left on the funnel paper and the mixture will be separated from the iron and sand in the beaker.

It will then be appropriate to use a magnet to separate the iron from the sand. However as the sand & iron will be wet, leaving the mixed solution of sand and iron to dry will be appropriate. Magnetic separation consists of using a magnetic to attract the ferromagnetic metal iron. As seen in figure 6, once attracting the iron from the sand, the iron will be on the magnet and very hard to separate from the magnet. Thus using glad wrap over the magnet the glad-wrap will be easily removed from the magnet as it is nonmagnetic and the iron fillings would be easily poured onto a watch glass.

Once extrapolating the obvious and simple substances from the mixture, it is then appropriate to separate the methylated spirits. Methylated spirits also known as ethanol is a alcohol which consists of a certain percent of methanol added to it to create a poisons drinking substance.

Methylated spirits is a polar molecule, its hydrogen’s, carbons and oxygen’s all distribute positively and negatively charges, thus creating a polar molecule. As Methylated spirits is polar it is miscible in water. Therefore as it is miscible in water the group will find filtering and decanting not an option to separate the methylated spirits from the water. Thus the group will use fractional distillation. However it is appropriate to explain why methylated spirits have a lower boiling point that Figure 7 water and this is all about the chemical structure of methylated spirits and water (H20).

Methylated spirits undergo a reaction to form a hydrogen bond. As hydrogen bonds form between Hydrogen’s and a highly electronegative atom namely, 0, F and N, methylated spirits fall into this category. Methylated spirits contain a hydrogen and a highly electronegative oxygen atom, thus the reaction of hydrogen bonding will occur, this is seen in figure 8.

Despite water is polar and also miscible in methylated spirits (metho) it does not have the same chemical structure as does methylated spirits. Water has a smaller structure and can continuously form hydrogen bonds thus enhancing its molecular strength as metho does not continue forming hydrogen bonds. This is shown in figure 9.

Both figure 8 and 9 show the difference between the hydrogen bonding of both metho and H20, it is evident that water consists of very strong intermolecular forces as it is continuously forming, however metho has less opportunity for hydrogen bonding, thus its formation in structure is weaker. Therefore it is evident that the metho will need less energy to deconstruct its chemical structure compared to water as it will need more energy to breakdown its strong hydrogen bonding. Therefore based on this information it will be efficient to use fractional distillation as methylated spirits will be evaporated and be collected as the dilute.

Fractional distillation is the method of separating mixtures into their original individual components based on boiling the substance that is wanting to be found boiling point. Therefore a thermometer is used to signify the what the temperature of the mixture is boiling at and as soon as it hits the boiling point of the substance wanting to be extrapolated, the gas then rises into a condenser and the condenser then condenses the gas back into a liquid, slowly dripping the liquid back into its original form. As methylated spirits has a lower boiling point (70-80 degrees)than water (100 degrees) it will be appropriate to use the fractional distillation method to find the amount of methylated spirits in the mixture.

Two substances that were left in the mixture were both sodium sulfate and sodium chloride. Both these salts are soluble in water due to their chemical structures.

Sodium chloride is well known as a halite (rock salt), salt which is situated in the oceans and is more chemically known as an ionic compound. As seen in figure 11, its chemical structure is very strong as it consists of an ionic bonding.

The lattice structure of the ionic bonding between the two compounds creates a very strong chemical structure. In return this defines why sodium has such a high boiling point of 1413 degrees as the chemical structure needs stacks of energy to break down the composition.

Sodium sulfate with the formula Na2SO, has an extremely similer structure as sodium chloride. At its solid form sodium sulfate forms a white crystal also known as a salt. Its ionic structure very alike to sodium chloride defines the reason why it also has a high boiling point of (…..). Both sodium sulfate and sodium chloride are soluble in water.

As H20 water is a polar molecule, in other words consists of uneven distribution of charges, the negatively charged oxygen the end of the water is attracted to the positive sodium ion in the salt. As seen in figure 12 the reaction shows the oxygen extracts the lattice structure of in this case sodium chloride, however also sodium sulfate. Therefore putting more water molecules surrounding the salt, enabling it to de-solve. (Wiki answers.com, year unknown).

NaCl(s) + H2O —> Na+(aq) +Cl-(aq) + H2O

Therefore no separation technique can be applied to either sodium sulfhate or sodium chloride as they are both salts and dissolve in water. As they both are miscible in water and impossible to decant, filtrate, evaporate or use fractional distillation. Creating one of the solutions to form a insoluble compound would be highly affected and would then be able to filtrate out.

To separate the NaCl & Na2SO4 from the mixture, it was evident to use a ionic compound that reacted with an opposite charge, such as +cation attracts -anion. Therefore Barium Chloride chemical formula BaCl has two separate ionic charges Ba2+ and Cl-. These two ions are attracted to their opposite charges when coming into contact with them. This can be seen in the formula below.

When adding BaCl to the mixture the following reaction will occur.

BaCl2 + Na2SO4 —— BaSo4 + 2Na+ CL-

The formula above represents the reaction of Barium and sulfate creating a solid, whereas the Na and Cl are left by themselves as spectators as they do not undergo a reaction.

This then creates a insoluble solution which can be filtrated out using the basic filtration method, as mentioned before regarding sand and iron.

Therefore analyzing the chemical and physical components of each substance that is present in the mixture, it was evident to what separation would be applicable to each substance; this can be seen in the flow chart below. It was then hypothesized that based on these physical and chemical properties, each substance would be extrapolated giving a 5% error range for any mistakes made throughout the experiment.

Flow chart

This flow chart represents what method for each substance was used to separate it from the mixture.

Apparatus

• Evaporating disk
• Separation funnel
• Filtration funnel
• Filter paper
• Boss clamp and Retort stand
• Measuring cylinder
• 5 Beakers
• 0.6g of Sodium Sulphate (Na2SO4)
• Atomic weight scales
• 13ml of Vegetable Oil
• Spatula
• Barium Chloride (BaCl2)
• 1.3g of Sodium Chloride (NaCl)
• Glad Wrap
• Electronic heating mantle
• 5 distillation-tube clips
• Round bottom flask
• Condensing tube
• Thermometer
• Stand
• Glass Rod
• Distillation tube
• 5.5g of Sand (SiO2)
• 2.4g of Iron fillings (Fe)
• Water (H2O)
• 25ml of Methylated Spirits
• Magnet

Method

The mixture was poured into a beaker using a stirring rod for more accuracy, separating the hexane from the mixture.

The hexane was then put into a separation funnel with the mixture beaker under the tap, to retrieve any droplets of water that were still in the hexane. Thus the hexane was completely separated from the mixture.

Filtration equipment was set up appropriately ready for use.

Sand & iron was poured through the filter paper (*2)

Beaker retrieved all the liquid, thus separating the iron and sand.

Sand & iron put on watch glass and left over night to dry; enabling separation.

Magnet covered in glad-wrap appropriately separated iron from sand.

Both Sand & iron were put on separate watch glasses.

Fractional distillation equipment set up appropriately.

Heat box turned on to boil the methylated spirits.

Thermometer used to signify the boiling point of methylated spirits.

Methylated spirits boiled and evaporated.

Methylated spirits went through condenser; gas underwent a physical change back to the liquid (methylated spirit).

Methylated spirits separated from mixture and placed in beaker.

Using calculations the amount of BaCl that was needed to react with Na2So4 was found

Using an electric weighing machine an exact value of Barium was then added to the mixture containing NaCl and Na2S04.

BaSo4 became insoluble in the mixture, thus setting up the filtration equipment was needed.

Filtration set up for separation

BaS04 separated using filtration with two funnel papers and a funnel.

BaS04 put on a watch glass for drying.

NaCl and water was left in the mixture, thus the use of evaporating was used.

Electric heater, a round bottom conical flask, condenser and tubes were set up to evaporate the water from the NaCl.

Water was placed into a separate beaker and then placed in the air drying area to evaporate any extra water, leaving an accurate solution of NaCl.

Discussion

This extended experimental investigation determined whether a substance can be separated effectively based on its chemical and physical components, allowing 5% to pass as an accurate result. Therefore analyzing the results in table into graphs will be most efficient to display the data.

Graph 1 compares actual mass to the experimental mass of only gram solutions. It is evident to note that all the mixtures despite the outliers barium sulfate and sodium sulfate are in an error range of 5-10%. The most accurate result was the iron fillings; 99.17% of the iron fillings were extrapolated from the mixture. The 2nd most efficient extrapolated data was the sodium chloride with 96% extrapolated. Sand was also quite efficiently extrapolated however only 89.45% was separated from the mixture. The two drastic outliers did however have a major effect on the hypotheses. As barium sulfate & sodium sulfate had only 50% separated from the mixture.

Analyzing graph 2 it is appropriate to suggest that the methods that were used to extrapolate methylated spirits and hexane may not have been most appropriate as there was in both hexane and methylated spirits 1 ml missing (4%). However despite this diminutive difference it is acknowledgeable to suggest that the techniques did work as 96% of both hexane and methylated spirits was extrapolated from the mixture. Therefore the hypothesis was proven correct as there was a 4% error. However it is recommended that if the experiment was to be done again different methods of separation may apply to both hexane and methylated spirits.

It is therefore appropriate to suggest that the hypothesis was proven wrong as the sand, barium sulfate and sodium sulfate all had more than a 5% error range. Many variable may have caused the inaccurate results of all substances, as it must be notable not one substance was fully extrapolated to 100%. Finding the right amount of each substance was extremely important as it then proved that mixtures can be separated based on their physical and chemical properties. The erroneous results create room for discussion into what may have caused the different result. One major variable may be the use of equipment.

Hexane was separated using decanting with a stirring rod and manually pouring the oil into another container, however there was 1ml of hexane missing the reason to why may been defined as not enough care when titrating or maybe the whole techniques was wrong itself.