INSTITUTE OF HEALTH SCIENCES

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INSTITUTE OF HEALTH SCIENCESPCT 112 LABORATORY REPORT

CHEMICAL BONDINGMOMPATI LETSWELETSEDATE OF EXPERIMENT: 28-01-2015

Surname: LetsweletseFirst names: MompatiID number: 3221Practical no: 1TITLE: EFFECTS OF CHEMICAL BONDING ON SELECTED PHYSICOCHEMICAL REACTIONS OF ORGANIC INORGANIC COMPOUDS.AIM: To demonstrate the effect the chemical bonding on selected physicochemical reaction of organic and inorganic compounds.THEORYAchemical bondis an attraction betweenatomsthat allows the formation ofchemical substancesthat contain two or more atoms. The bond is caused by theelectrostatic force of attraction between opposite charges, either betweenelectronsandnuclei, or as the result of adipoleattraction. The strength of chemical bonds varies considerably; there are "strong bonds" such ascovalentorionic bondsand "weak bonds" such asdipole -dipole interactions, theLondon dispersion forceandhydrogen bonding.Since opposite charges attract via a simpleelectromagnetic force, the negatively chargedelectronsthat are orbiting the nucleus and the positively chargedprotonsin the nucleus attract each other. An electron positioned between two nuclei will be attracted to both of them and the nuclei will be attracted toward electrons in this position. This attraction constitutes the chemical bond. Due to thematter wavenature of electrons and their smaller mass, they must occupy a much larger amount of volume compared with the nuclei, and this volume occupied by the electrons keeps the atomic nuclei relatively far apart, as compared with the size of the nuclei themselves. In general, strong chemical bonding is associated with the sharing or transfer of electrons between the participating atoms. The atoms inmolecules,crystals,metalsand diatomic gases indeed most of the physical environment around us are held together by chemical bonds, which dictate the structure and the bulk properties of matter. As an example using ionic and covalent bonding, Ionic bonding (transferring of electrons between atoms to fulfill their electron configuration) has high boiling and melting points due to strong bonds between them hence very large energy is required to break free bonds. This strong bond also affects the solubility due to ionization of molecule that is electrons are not equally shared on the other hand Covalent boding has weak bonds which are easily broken down hence low melting and boiling point since no much energy is required to break the weak bonds.The strength of a bond in a substance affects the melting point, the boiling point, the hardness and the flexibility of the substance. It also determines electrical conductivity. MaterialsMATERIALS 50 ml beakers Test tubes Spatula Measuring cylinder Spatula Test tube 10ml measuring cylinder PH meter Litmus paper blue Universal indicator paper Distilled water Ethanol Chloroform 0.2M of ethanol, hydrochloric acid and Ethanoic acid

BOILING POINT)RELATIVE MOLECULAR MASS (g/mol)STRUCTURAL FORMULA FOR

Water10018.015

Methanol64.7 32.042

Ethanol7846.068

chloroform61,2119.518

PROCEDURE

TASK 1: BONDING AND BOILING POINTSThe boiling points of water, methanol, ethanol and chloroform were noted from one source their relative molecular masses were calculated.

TASK 2: SOLUBILTY OF IODINE IN DIFFERENT LIQUIDS A small crystal of iodine was put in a test tube.5ml of distilled water was poured and the mixture was shaken. The above step was repeated with ethanol and chloroform. Changes in terms of solubility and color change were noted.TASK 3: MISCIBILITY OF LIQUIDS 10 ml of water was mixed with 10ml of ethanol in 50ml beaker. The previous step was repeated with water and chloroform and ethanol and chloroform. Changes in terms of temperature were noted and the miscibility of substances was recorded.TASK 4: ACIDIC PROPERTIES OF ETHANOIC ACIDThe volume required to prepare 0.2M of ethanol was calculated using the information provided. The calculated volume was measured using the measuring cylinder henceforth was diluted in the bottom flask to fill up to the 1000ml mark in preparation of 0.2M ethanol. the pH of prepared 0.2M ethanol was measured using the universal indicator ,litmus blue paper and a pH meter .The previous steps were repeated for the solution of HCl and ethanoic acid. The results were noted and comparison in terms of acidity was noted among concerned solutions.RESULT AND ANALYSIS

TASK 1: BONDING AND BOILING POINTSCALCULATIONSH: 1.008, O: 16.00, C: 12.01, CL: 35.45 Structural formula for water

Relative molecular mass :( 1.008+16.00=18.016g/molMethanolStructural formula for ethanol

(1.008+16.00+12.01=32.042g/mol

EthanolStructural formula for ethanol(1.008+ (12.0116.00=46.068g/mol

ChloroformStructural formula for chloroform.(35.5

According to the results in the above table it clearly showing that water has the highest boiling point and the smallest relative molecular mass followed by Ethanol and methanol respectively with chloroform being the last with lowest boiling point and a large relative molecular mass.TASK 2: SOLUBILTY OF IODINE IN DIFFERENT LIQUIDSThe obtained results shows that iodine is not soluble in water and on the other hand is partially soluble chloroform. They also indicate that iodine is completely soluble in ethanol with a perceptible color change.TASK 3: MISCIBILITY OF LIQUIDS According to experimental results from task 3 it was observed that the mixture of ethanol and chloroform, ethanol and water were miscible with a slight temperature change compared to the mixture of water and chloroform which showed two substances (water and chloroform) being immiscible and showed no temperature change

TASK 4: ACIDIC PROPERTIES OF ETHANOIC ACIDObtained result shows that the PH of ethanol is 7 and 7.680 using universal indicator and PH meter respectively, the blue litmus paper remained blue when it was dipped into Ethanol. With HCL the PH was noted to be 1 and 0.976 using universal indicator and PH meter respectively it was found that HCL turned the blue litmus paper to red, on the other hand it was recorded that Ethanoic acid has the PH of 3 and 3.060 using universal indicator and PH meter respectively, it was also observed that Ethanoic acid turned the blue litmus paper red.

DISCUSSIONTASK 1: BONDING AND BOILING POINTSWATER:The molecular formula for water is H2O it indicates that water is composed of two hydrogen atoms and one oxygen atom In water, each hydrogen nucleus is covalently bound to the central oxygen atom by a pair of electrons that are shared between them. In H2O, only two of the six outer-shell electrons of oxygen are used for this purpose, leaving four electrons which are organized into two non-bonding pairs.The four electron pairs surrounding the oxygen tend to arrange themselves as far from each other as possible in order to minimize repulsions between these clouds of negative charge. This would ordinarily result in a tetrahedral geometry in which the angle between electron pairs (and therefore the H-O-Hbond angle) is 109.5. However, because the two non-bonding pairs remain closer to the oxygen atom, these exert a stronger repulsion against the two covalent bonding pairs, effectively pushing the two hydrogen atoms closer together. The result is a distorted tetrahedral arrangement in which the HOH angle is 104.5.henceforth the presence of hydrogen interaction means much energy is required to break the bond hence a high boiling point of about 100.METHANOLMethanol is an alcohol which possesses only one carbon bonded to hydroxyl group and 3 hydrogens. It has high boiling point due to Hydrogen bonding .Hydrogen bonding occurs between molecules where the hydrogen atom is attached to one of the very electronegative elements - fluorine, oxygen or nitrogen in this case is oxygen .Hydrogen bonding isn't the only intermolecular force in Ethanol. There are also van der Waals dispersion forces and dipole-dipole interactions. Therefore much energy is required to break apart this bonds .Because of the one hydrogen bond, the boiling point becomes lower than that of water.ETHANOL Ethanol is a 2-carbon alcohol. Its molecular formula is CH3CH2OH. An alternative notation is CH3CH2OH, which indicates that the carbon of a methyl group (CH3) is attached to the carbon of a methylene group (CH2), which is attached to the oxygen of a hydroxyl group (OH).Like in other alcohols, Ethanol also consists of a hydroxyl bond which accounts for its high boiling point in this case the boiling point of ethanol is higher than that of methanol because as the number of carbon atoms in the chains increases so does the bonds hence the boiling point also increases. It takes more energy to overcome the dispersion forces, and so the boiling points rise.CHOROFORMChloroform is considered to be nonpolar molecule even though it has some polar bonds. Having carbon surrounded by 3 chlorine atoms and one hydrongen.No hydroxyl group bond has less energy to break the bonds.

TASK TWO: SOLUBILITY OF LIQUIDS IODINE AND WATERNon-polarIodineis not verysoluble in water according to obtained results. This is due to intermolecular bond between an induced dipole (I2) and a polar bond inwater which is not very strong compared to the hydrogen bonds inwater. Thewatermolecules remain hydrogen bonded to each other, and not allowing an iodinemolecule come between them. IODINE AND ETHANOLI2 is a nonpolar molecule, and will more easily dissolve in a nonpolar solvent. Despite its immiscibility with water, the ethanol molecule has characteristics in common with other nonpolar solvents. This allows iodine molecules to be more easily dissolved in ethanol, other alcohols and solvents like benzene or acetone hence the reason for the obtained results which saw iodine being soluble in Ethanol with a color change

IODINE AND CHLOROFORM Chloroform/tetrachloride is one the compounds which are nonpolar containing also polar bonds. The bonds between the carbon and each chlorine are polar. But there is no negative end to the molecule and no positive end rather ,the outer part is negative and the inner part positive(partially)so the molecule is nonpolar ,In general symmetrical molecules are non polar even though they may contain polar bonds. The polar bonds present in the chloroform molecule made iodine to be partially soluble in chloroform. TASK 3: MISCIBILTY OF LIQUIDSETHANOL AND WATEREthanol an alcohol is an organic compound its polar groups attached to a nonpolar framework of carbon and hydrogen atoms. Ethanol contains the polar OH group. The O-H bond is able to form hydrogen bonds. Ethanol molecules can form hydrogen bonds with water molecules as well as with each other .As a result the solute-solute, solvent solvent forces are not greatly different in a mixture of ethanol and water. No major change occurs in the environment of the molecules as they mixed. Therefore the increased entropy when the components mix plays a significant role in solution formation and ethanol is completely miscible with water. The warmth felt on the beaker was due to breaking of bonds showing that it was an exothermic reaction.

WATER AND CHLOROFORMChloroform is considered to be an organic (nonpolar) solvent. It has low solubility in water (they aren't miscible) Water will try to surround the non-polar molecule and try to attract them apartFrom each other, but all this does it forms a stronghydrogen bond, or, intermolecularforceamong the water molecule. The non-polar compound cannot join the bonds of the water molecule because of its weak attraction and theabsenceof dipoles. They do not have negative and positive ends. The non-polar molecules become neutralamongthe water, and the waters attractive bonds with each other then push the non-polar compound away andseparatefrom them.Hencerforth this accounts for obtained results having water not miscible with chloroform.ETHANOL AND CHLOROFORMChloroform is considered to be an organic (nonpolar) solvent. It has hasweak polarity, and thus it will dissolve some moderately polar molecules, henceforth ethanol is miscible because of the polar bonds present in chloroform.TASK 4: ACIDIC PROPERTIES OF ETHANOIC ACIDHydrochloric acid and Ethanoic acid according to the PH meter and universal indicator paper are shown to be acidic or to have acidic properties. This is because their PH ranges their ranges from 0.976 to 3.060on the meter and they turned the blue litmus paper pink. These is due to the hydrogen ions(H+) , they are more concentrated than the OH-.Ethanol showed basic properties, the blue litmus paper remained blue and the PH and the universal indicator paper readings ranged from 7.94 to 8.This is due to high.ANSWEARS TO QUESTIONS1) Would you classify Ethanoic acid as a weak or strong acid? Justify your answerAs a weak acid because it has a pH of 3 which is the range of weak acids. A weak acid is one which doesn't ionize fully when it is dissolved in water.Therefore it undergoes partial ionization when it is dissolved in water. Ethanoic acid is a typical weak acid. It reacts with water to produce hydroxonium ions and ethanoate ions, but the back reaction is more successful than the forward one. The ions react very easily to reform the acid and the water.CH3COOH + H2O CH3OO- + H3O+

2) Explain the difference in acidic strength between ethanol and Ethanoic acid.

The strength of any acid comes from how easily a "proton" is lost to water. Dissociation is a "competition" between the acid molecule and water. Strong acids are "easily defeated". The water molecule has a greater affinity for H+ than does the strong acid anion.

But in a weak acid, the hydrogen is more strongly bound to the "anion". In the -COOH structure the electron density is shifted toward the doubly bonded oxygen and away from the hydrogen making it more easily lost to adjacent water molecules.

In ethanol, there is no electron withdrawing atom and the bond between O and H is much stronger, making the H less easily removed by adjacent water molecules. In fact, the O-H is so strong; the ethanol barely behaves like an acid at all.

3) How would you prepare 2.0l of 0.1M of HCL?

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