POINT LISAS CAMPUS
Esperanza Road,
Brechin Castle,
Couva
www.utt.edu.tt
LAB 1
Decomposition reaction

Aim: Determination of the number of moles of water molecules of crystallization present in hydrated Magnesium Sulphate (MgSO4.xH2O) Apparatus: Mass balance, test tube, test tube holder, heat-proof mat and bunsen burner. Reagents: Hydrated sodium carbonate. Theory: Chemical decomposition, analysis or breakdown is the separation of a chemical compound into elements or simple compounds. A more specific type of decomposition is thermal decomposition or thermolysis, which is caused by heat. ABA+B, the reaction is endothermic, since heat is required to break the chemical bonds. Most decomposition reaction require energy either in the form of heat, light or electricity. Absorption of energy causes the breaking of the bonds present in the reacting substance which decomposes to give the product. When a hydrated salt is heated it decomposes into a pure form of the salt and water. MgSO4.xH2O MgSO4 + H2O

Procedure: Refer to Handout Results: A. Mass of test tube/g = 21.77 B. Mass of the tube and salt/g = 24.0 A table showing the mass of the test tube and salt after 3 consecutive heating: Heating | Mass of the test tube and salt/g | 1st | 23.96 | 2nd | 23.81 | 3rd | 23.81 |

Calculations: G. Mass of anhydrous magnesium sulphate/g = F - A = 23.81 – 21.77= 2.04 H. Mass of water of crystallization evaporated/g = B – F = 24.0 – 23.81= 0.19 I. Number of moles of anhydrous magnesium sulphate = _____G____ Mr (H2O) _____2.04____ = 2.04 24+32+4(16) 120 = 0.017 moles

J. Number of moles of water = ____H____ Mr (H2O) = 0.19 = 0.01 moles 18

Discussion: Limiting this experiment were sources of errors which was human error. The environment was not control where water in the formula water vapor was still in the atmosphere. In the process and limited time of the cooling solid, same water could have been reabsorbed affecting the true accuracy of the mass of the water of crystallization in the solid. The measurement of the salt along with the apparatus has a source of error of about 0.05 because of a draft affecting the scale. Chemical decomposition, analysis or breakdown is the separation of a chemical compound into elements or simpler compounds. It is sometimes defined as the exact opposite of a chemical synthesis. Chemical decomposition is often an undesired chemical reaction. The stability that a chemical compound ordinarily has is eventually limited when exposed to extreme environmental conditions like heat, radiation, humidity or the acidity of a solvent. The details of decomposition processes are generally not well defined, as a molecule may break up into a host of smaller fragments. Chemical decomposition is exploited in several analytical techniques, notably mass spectrometry, traditionalgravimetric analysis, and thermogravimetric analysis. There are three broad types of decomposition reactions: thermal, electrolytic and catalytic Conclusion: the number of moles of water of crystallization present in hydrated magnesium sulphate is calculated to be 0.01

POINT LISAS CAMPUS
Esperanza Road,
Brechin Castle,
Couva
www.utt.edu.tt

LAB 2
Volumetric Analysis

Aim: Determination of the concentration of an unknown alkali solution by titration Apparatus: (3) 100ml conical flasks, (2) 150ml beakers, 1 small funnel, (1) 50ml burette, (1) 25ml pipette, 1 pipette bulb, (1) 500ml bottle of distilled water, 1 retort stand with clamps, 1 white tile.

Reagents: unknown NaOH solution, 0.2M HCl solution, screened methyl orange.

Theory: Volumetric analysis, any method of qualitative chemical analysis in which the amount of a substance is determined by measuring the volume that it occupies or, in broader usage, the volume of a second substance that combines with the first is known proportions, more correctly called titrimetric analysis or titration.

Procedure: Refer to Handout Results: A table showing the volume of acid used to neutralize the base.

Reading | Intial | Final | 1st | 0 | 26.0 | 2nd | 0 | 25.7 | 3rd | 0 | 26.8 |

Calculation: Average volume of acid = (26.0 + 25.7 + 26.8) ÷ 3 = 26.17 Equation: HCl + NaOH NaCl + H2O Volume of Hcl required = 26.17cm3 Volume of NaOH = 25cm3 HCl – 0.2mol/dm3 Number of moles of HCl = 26.17 x 0.2 = 0.0052 1000 Mole ratio HCl : NaOH 1 : 1 0.0052: 0.0052 mols 25ml of NaOH = 0.0052 mols Molar concentration = 0.0052 x 1000 25 =0.2 mol/dm3 = 0.2M

Questions: 1. Write a balanced chemical equation for the reaction occurring. HCl + NaOH NaCl + H2O 2. Determine the volume of acid required to neutralize 25ml of NaOH. Volume of acid required is equal to average Average = 26.17 3. Determine the number of moles of acid used to neutralize the NaOH. The NaOH = 26.17 x 0.2 = 0.0052mols 1000 4. Determine the number of moles present in 25ml of NaOH. It is a one to one ratio. Therefore the number of moles = 0.0052mols 5. Determine the number of moles present in 100ml of NaOH and hence the concentration of the NaOH. The number of moles in 1000ml = 0.0052 x 1000 = 0.21 moles 25 Molar concentration = 0.21 M

Discussion: Sources of error limiting the effectiveness of the experiment is human error. Since the titration method involves total human involment procedures from using the burette in adding the HCl in the flask to a proper reading, using the meniscus could be affected. Improper cleaning of instruments so therefore off spec results. Stirring of the flask is another issue where as the solution does not get a proper mixture. Titration, by definition, is the determination of rank or concentration of a solution with respect to water with a pH of 7. Volumetric analysis originated in late 18th-century France. François-Antoine-Henri Descroizilles developed the first burette (which was similar to a graduated cylinder) in 1791.[5] Joseph Louis Gay-Lussac developed an improved version of the burette that included a side arm, and coined the terms "pipette" and "burette" in an 1824 paper on the standardization of indigo solutions. A major breakthrough in the methodology and popularization of volumetric analysis was due to Karl Friedrich Mohr, who redesigned the burette by placing a clamp and a tip at the bottom. Acid-base titrations depend on the neutralization between an acid and a base when mixed in solution. In addition to the sample, an appropriate indicator is added to the titration chamber, reflecting the pH range of the equivalence point. The acid-base indicator indicates the endpoint of the titration by changing color. The endpoint and the equivalence point are not exactly the same because the equivalence point is determined by the stoichiometry of the reaction while the endpoint is just the color change from the indicator. Thus, a careful selection of the indicator will reduce the indicator error. For example, if the equivalence point is at a pH of 8.4, then the Phenolphthalein indicator would be used instead of Alizarin Yellow because phenolphthalein would reduce the indicator error. Common indicators, their colors, and the pH range in which they change color are given in the table above.[14] When more precise results are required, or when the reagents are a weak acid and a weak base, a pH meter or a conductance meter are used.

Conclusion: The concentration of the unknown alkali, Sodium hydroxide using titration or method is calculated to be 0.21M

POINT LISAS CAMPUS
Esperanza Road,
Brechin Castle,
Couva
www.utt.edu.tt

LAB 3
Rate of reaction

Aim: Determine the rate of reaction upon changing the concentration of the reactant.

Apparatus: (2) 100ml beakers, 250ml beaker, stirring rod, (2) 25ml graduated cylinder, stopwatch, white paper

Reagents: 0.15M sodium thiosulphate, 6M HCl solution, distilled/deionised water

Theory: For many reactions involving liquids or gases increasing the concentration of the reactants increases the rate of reaction. In a few cases, increasing the concentration of one of the reactants may have little noticeable effect of the rate. In order for any reaction to occur, those particles must first collide. This is true for both particles in a solution or if one is in solution and the other a solid. If the concentration is higher, the chances of the collision are greater.

A diagram of the setup of the apparatus used

Procedure: Refer to handout

Results:
A table showing the time taken for sodium thiosulphate to react with hydrochloric acid at different concentrations Test | Volume of sodium Thiosulphate (ml) | Volume of distilled or deionised water (ml) | Time (s) | 1 | 25 | 0 | 52.8 | 2 | 20 | 5 | 54.9 | 3 | 15 | 10 | 104.5 | 4 | 10 | 15 | 166.1 |

Discussion: The rate of reaction or speed of reaction for a reactant or product in a particular reaction is intuitively defined as how fast or slow a reaction takes place. For example, the oxidation of iron under the atmosphere is a slow reaction that can take many years, but the combustion of butane in a fire is a reaction that takes place in fractions of a second. There are several factors that affect the rate of reaction of substances. These include; concentration of reactants, temperature, presence of catalyst and surface area.
Collision theory is a theory proposed independently by Max Trautz in 1916 and William Lewis in 1918, that qualitatively explains how chemical reactions occur and why reaction rates differ for different reactions. The collision theory can only occur when the suitable particles of the reactant hit with each other. Only a certain percentage of the sum of the collisions causes any noticeable or significant chemical change; these successful changes are called successful collisions. The successful collisions have enough energy, also known as activation energy, at the moment of impact to break the preexisting bonds and form all new bonds. This results in the products of the reaction. Increasing the concentration of the reactant particles or raising the temperature, thus bringing about more collisions and therefore many more successful collisions, increases the rate of reaction. When a catalyst is involved in the collision between the reactant molecules, less energy is required for the chemical change to take place, and hence more collisions have sufficient energy for reaction to occur. The reaction rate therefore increases.
In the lab since we were using hydrochloric acid the use of goggles and lab coat was worn. At all times whilst using the acid we were careful not to get it on our hands if it was spilled we would wash our hands thoroughly with soap. In order to reduce any errors variables were kept constant and the use of linear equipment was used. Measurements of the reagents were done by one person who took all values at eye level to avoid parallax error. The same cross was used throughout the experiment however, different members where conducting the experiment during each test therefore there might have been human errors. The same shape and size of beaker was also used to prevent errors.
You can see that as the concentration decreases the rate of reaction decreases because as the concentration decreases there is a lower percentage of reacting molecules, meaning that the reaction between Sodium Thiosulphate will occur slower as there are less of these reacting particle decreasing the chances of a successful collision between them. This is shown on the graph by a descending curve.
We could have improved accuracy by using mechanical pipettes to measure the reagents. Also the experiment could have been repeated further so that we could have obtained even more reliable results. Possible experiments that could be done to further support the theory are perhaps repeat the experiment but this time change the concentration of the hydrochloric acid. Also the experiment could be done in a situation where the undependable variables could be controlled.

Conclusion: In conclusion it appears that as the concentration of the sodium thiosulphate decreases the rate of reaction decreases.

POINT LISAS CAMPUS
Esperanza Road,
Brechin Castle,
Couva
www.utt.edu.tt

LAB 4
Organic Chemistry

Aim: To identify the functional groups present in organic compounds

Apparatus: Bromine solution, Acidified potassium dichromate(VI), Universal indicator, Cyclohexane, Cyclohexene, Ethanol, Ethanoic Acid, Ethylamine, Test tubes, Hotplate and large beaker of water for warming

Theory: Organic chemistry is that branch of chemistry that deals with the structure, properties and reactions of compounds which contain carbon. A series of organic compounds that have similar structural features but differ from adjacent members by -CH2 group is referred to as homologous series. Members of the same homologous series have the same functional group. Compounds containing the same functional group undergo the same or similar chemical reactions. Members of the alkane group which contain carbon to carbon single bonds only undergo substitution reaction with bromine only in the presence of bright UV rays. In light the solution should change from brown to colourless. Alkanes are too inert to be oxidized. Alkenes on the other hand which have the presence of the carbon to carbon double bond functional group undergo halogenations reaction with bromine in both dark or light and the solution also changes from brown to colourless. Alkenes can also be oxidized to some extent by acidified potassium dichromate(VI). Alkanols have the functional group -OH. Alkanols are oxidized by acidified potassium dichromate(VI) the solution changes from an orange colour solution to green due to the presence of chromium(III) ions. Alkanoic acids contain the functional group –COOH. Acids when exposed to universal indicator changes to red, orange or yellow. Red indicates it is a strong acid and yellow or orange a weak acid. Amides belong to the functional group RnE(O)xNR'2. Amides are very weak bases therefore they react to universal indicator by changing to a blue colour.

Procedure:
Refer to handout

Results:
A table showing the observations and inferences made

Sample | | Observations | | Bromine Solution in Sunlight | Bromine Solution in Dark | Acidified Potassium Dichromate (VI) | Universal Indicator | Interpretation | Homologous series and functional group | A | Solution clear, colourless | Solution clear, colourless | Clear with orange precipitate | Orangish precipitate | C6H10 + Br2 C6H10Br2 + Br2 The equation shows that Halogenation occurred. | Compound belongs to alkene group which contain carbon to carbon double bonds. | B | Solution colourless/insoluble | Solution clear, colourless | Clear and immiscible | Light Orange/ immiscible | C6H12 + Br2 C6H10Br2Substance B showed no reaction with acidified potassium dichromate. | Compound belongs to the alkane group which contain carbon to carbon single bonds. | C | Solution brown(beige) in colour | Solution brown (beige) in colour | Solid dark orange solution | Blood red | The colour change to blood red indicates that it is a strong acid. | Compound belongs to Alkanoic acids containing the functional group –COOH | D | Solution colourless | Solution colourless | Colour change from brown to orange to green | Orange | Oxidation occurred where the solution changed to green when exposed to acidified potassium dichromate | Compound belongs to Alkanols and contain the functional group –OH | E | Solution colourless | Solution colourless | Mustard yellow | Dark Blue | The colour change to dark blue indicates that is a weak base. | Compound belongs to Amides and contain the functional group RnE(O)xNR'2 |

Conclusion: In conclusion Sample A is determine to belong to the alkene group therefore it is cyclohexene. Sample B is determine to belong to the alkane group therefore it is cyclohexane. Sample C is determine to belong to alkanoic acid group therefore it is ethanoic acid. Sample D id determine to belong to the alkanol group therefore it is ethanol. Sample E belongs to the amide group therefore it is ethylamide.