lab inorganic 8

ITEM	CONTENT	MARKS
Objective	The purpose of this experiment is to determine the concentration of an unknown  copper(II) solution by spectrophometric analysis.
Introduction	The intensity of the colour is proportional to the concentration of the species in the solution . We can see the colour as a complement of the visible wavelength being absorbed by a sample . Substances that appear red and absorbed blue visible light and reflect other visible colours to our eyes vice versa to the substances that absorbed red appear as blue light.Absorption of light is more related to available energy levels in the molecule or an ion.The amount of energy and therefore the wavelength of radiation involved in this transition is a function of the electronic structure of molecule or an ion.            The spectronic 20 colourimeter is an versatile instrument that is useful for spectrophotometric or colourimetric determinations of solutions.Spectrometric is difficult because concentrations is very low. If the ions do not produce an intensely coloured complex ,Cu(NH3)42- , by the addition of of concentrated aqueous ammonia .The absorbance at various concentrations is used to plot graph for the determination of the concentration of copper(II) ions in an unknown solutions.
Results	Test tube number Concentration (M) Absorbance 1 0.000 0.055 2 0.060 0.251 3 0.140 0.397 4 0.200 0.582 5 0.00153 0.060 6 0.00092 0.058
Discussion	Spectrochometry has very wide range of application .Absorbance has the value that obtained by determining the amount of light of certain wavelength that absorbed by samples . 1)graph paper at the back shown the line grah of concentration versus absorbance graph. 2)Given 0.2 M Cu2+ solution  mv = mv ( 4/1000) x 0.2 = 0.01 M M = 0.08 M mv=mv (7/1000) x 0.2 = 0.01 M M = 0.14 M 3)Y = mx + c At point (0.000,0.055) 0.055 = (0.000 x m) + c C = 0.055 At point (0.060 , 0.251) 0.251 = (0.060 x m) + 0.055 M = 3.267 Y = 3.267x + 0.055 4)Beer’s Law : Concentration unknown = absorbance – intercept                                                  slope concentration unknown = 0.060 -0.055                                           3.267                                       = 0.0015 Concentration unknown = 0.058-0.055                                              3.267                                        =0.00092 5) As we know that the Beer’s Law state that the absorbance is directly proportional to the concentration , the resulting graph yields a straight line . The equation line which is Y = 3.267x + 0.055 can be used to determine the the concentration of an unknown solution .
Conclusion	The concentration of an unknown copper(II) solution by spectrophotometric analysis was determined. The concentration is 0.00153 M and 0.00092 M .
References	1)    http://www.utc.edu/Faculty/Gretchen-Potts/chemistryhelp/beers.htm 2)    http://biomed.engr.sc.edu/bme_lab/lab%20reports/58)%20Determination%20of%20Protein%20Concentration%20using%20Spectrophotometry.pdf

inorganic 2

ITEM	CONTENT	MARKS
Objective	The purpose of this experiment is to perform qualitative analysis to identify transition metal cations
Introduction	Qualitative analysis is the determination of the types of ions present in a solution.Confirmatory tests are to determine conclusively that a certain ion is present.Intefering ions is removed before proceed with the cofirmatory test.         In this experiment we are using mixture that is provided by lab assistant.First we are separating the ion in the mixture by using HCl solution.          After they have been separated , the identification of each transition metal cation depends of the observation of a characteristics chemical reaction.From the characteristics we can determine what kind of metal ion present in the mixture.
Results	1) On adding HCl to the mixture sample Observation Cloudy blue solution formed Balanced chemical equation Cu2+(aq) + H2S(aq)                CuS(s) + H2O(lq) Supernatant is formed 2) On adding H2S Obsevation Brownish precipitate with cloudy solution formed Precipitate and supernatant was formed, so we that there is present Cu2+ and Zn2+ in the mixture. Balanced chemical equation Cu2+(aq) + S2-(aq)                CuS(S) RESULT FOR CONFIRMATORY TEST FOR Cu2+ a)On adding  HNO3 Observation Black precipitate was formed Balanced chemical equation 3CuS(S)+8H+(aq)+2NO3-(aq)           3Cu2+(aq)+2NO+(aq)+3S(S)+4H2O(lq) b)On adding NH3,HNO3,and K4Fe(CN)6 Observation Brown precipitate was formed Balance chemical equation 2Cu2+(aq) + Fe(CN)64-(aq)           Cu2[Fe(CN)6](S) Therefore presence of Cu2+ was confirmed. RESULT FOR COFIRMATORY TEST FOR Zn2+ a)On adding HCl , NH3  and thioacetamide Observation Black precipitate was formed Balance chemical equation Zn2+(aq)+s2-(aq)          ZnS(s) b)On adding NH3,CH3COOH AND K4Fe(CN)6 Observation Brick red precipitate was formed Balance chemical equation 3Zn2+(aq) + 2Fe(CN)64-(aq)        Zn3[Fe(CN)6]2(s) Therefore presence on Zn2+ was confirmed.
Discussion	This experiment involving the qualitatives analysis which contain one or more metal cations.Several specific reactions will be carried out on solutions that will either separate the ions from each other to confirm the presence of particular ion.The reactions that confirm the presence of a particular ion involve the creation of visible product such as precipitates or coloured species .The reaction that involves the precipitation also be applied in the reaction.Qualitatative analysis rection is simple reaction because we identify only one ion for each time.         For the first experiment , HCl was used to precipitate Cu2+ as while as precipitate as CuS.This can be shown by balance chemical equation : Cu2+(aq) + H2S(aq)                CuS(s) + H2O(lq) From the observation supernatant was formed.After that we add H2S and the observation is brownish precipitate with cloudy solution formed. From the observation we know that supernatant and black precipitate was formed.So we separate the supernatant and the precipitate into different test tube.        Now we are discussing about the confimatory presence of Cu2+ first.The brownish precipitate was formed in this reaction can be showned by the balance equation below : Cu2+(aq) + S2-(aq)                CuS(S)          After that we add HNO3 into the soluition and boil several minutes to make sure the reaction was completed.The black precipitate was formed.This reaction can be showned by the equation below: 3CuS(S)+8H+(aq)+2NO3-(aq)  3Cu2+(aq)+2NO+(aq)+3S(S)+4H2O(lq)       After we centrifudge the solution , the precipitate was discarded.6 M NH3,6M HNO3 and K4Fe(CN)6 was added.Brick red precipitate was formed.This reaction can be showned by the chemical equation below : 2Cu2+(aq) + Fe(CN)64-(aq)           Cu2[Fe(CN)6](S) There from the equation and observation , the presence of Cu2+ was confirmed.       Now we are discussing about the presence of Zn2+.After adding HCl , NH3 and thioacetamide black precipitate was formed.The chemical reaction can be showned as below: Zn2+(aq)+s2-(aq)          ZnS(s) After we add with another one drop of HNO3 black precipitate was formed.Next we are adding NH3 , CH3COOH and K4Fe(CN)6 , brick red preciptate was formed.This can be showned by the balanced chemical equation below :  3Zn2+(aq) + 2Fe(CN)64-(aq)        Zn3[Fe(CN)6]2(s)        There is some precaution that we should be aware.First makesure that our test tube that we are going to use is very clean and do not touch the tip of any dropper to any other test or other solution , it is because it may cause contamination.  We know that many chemical in the laboratory are toxic , we should wearing gloves for handling it and be careful not spill at our skin and do not smell the chemicals . This chemical may harmed us .
Conclusion	As we know qualitative analysis involves the identification of the substances in a mixture ,  so the qualitative analysis was performed.From the experiment above the mixture containing Cu2+ ion and Zn2+ ion.
References	1)

THIN LAYER CHROMOTOGRAPHY OF ANALGESIC DRUGS

Objectives

1)    Determine the R_f value.

2)    To identify the components in the analgesic tablet by a TLC comparison 1with standard compounds.

Introduction

            Chromatographic are used extensively in organic chemistry laboratories for routines analysis. Thin layer chromotography (TLC) can be used to determine the purity of compound , to analyze the composition of a mixture are differentiated by exposing to two competing phases , the stationary phase is a polar adsorbent such as silica gel or alumina , which has been coated on plastic plate. The mobile phase is an organic solvent .The solvent moves up the plate capillary action.

            As the solvent moves past the spot that was aaplied an equilibrium was achieved for each component of the mixture between the molecules of that component which are adsorbed on the solid and the molecules which is are in solution . In principle , the components will differ in solubility and in the strength of their adsorption to the adsorbent and some components will be carried further up the plate than the others.When the solvent has reached on the top of the plate, the plate will be removed from the solvent , it will dried and the developing components will be visualised . UV lamp and iodine are used to visualized the components .

            In this experiment the TLC was used to examine the composition of known analgesic whic is the pain relieving drug such as paracetamol. Several common analgesics are aspirin and acetomeniphen . Caffein is sometimes added to these formulations to overcome drowsiness.

            The distance travelled by each component is measured and this value is called the retardation factor which is designated as R_f value.R_f value for a component is calculated using the following expression :

R_f  =  Distance traveled by the component

            Distance traveled by the solvent

There is some chemicals that we are using in this experiment are shown below.

Acetaminophen

Aspirin

Caffeine

Result and observation

Label	A (aspirin)	B (upthamol)	C (caffeine)	D (acetaminophen)
Reading 1 - Distance travelled from start line to center spot(cm)	2.6 cm	2.3 cm	1.1 cm	2.5 cm
Reading 2 - Distance travelled from start line to center spot(cm)	2.8 cm	2.4 cm	1.1 cm	2.4 cm

   

(TLC reading 2)                                   (TLC reading 1)

The distance from starting point to the end point of reading 1  is 5 cm while for reading 2 is 5.1 cm

R_f  =  Distance traveled by the component

            Distance traveled by the solvent

Calculation for reading 1

R_f of A (aspirin) =  2.6 / 5 = 0.52

R_f of B (upthamol) = 2.3 / 5 = 0.46

R_f of C (caffeine) = 1.1 / 5 = 0.22

R_f of D (acetaminophen) = 2.5 / 5 = 0.5

Calculation for reading 2

R_f of A (aspirin) =  2.8 / 5.1 =0.55

R_f of B (upthamol)  = 2.4 / 5.1 = 0.47

R_f of C (caffeine) = 1.1 / 5.1 = 0.22

R_f of D (acetaminophen) = 2.4 / 5.1 = 0.47 

The TLC reports that the drug containing is caffeine

Discussion

            Thin layer chromotography is a special of adsorption in which thin layer of adsorbent supported on a flat surfaces is utilized instead of a column of adsorbent , in a simple words thin layer chromatography techniques is used to separate mixtures.Thin layer chromotography techniques was performed on a sheet of glass or aluminium foil which is coated with thin layer adsorbent material usually silica gel.This layer was known as stationary phase.Silica gel is a form of silicon dioxide , the silicon atoms are joined via oxygen atoms in a giant covalent structure .However at the surface of the silica gel , the silicon atoms are attached to hydroxyl group . The surface of the silica gel is very polar , this is because of the hydroxyl igroup it can formed hydrogen bonds with suitable compounds around it as well as van der waals dispersion forces and dipole-dipole attraction.

            Differrent compounds in the sample mixture travel at different rates due to the differances in their attraction to the stationary phase and because of differences in solubility in the solvent . Fom the above calculation we can see that different compound has different R_f value.

            For reading 1 , R_f for aspirin is 0.52 , upthamol is 0.46 , caffein is 0.22 and acetaminophen is  0.5 . From reading 2 R_f value for aspirin is 0.55 , upthamol is 0.47 , caffein is 0.22 and acetaminophen is 0.47 . Reading 1 and 2 has same reading R_f value for caffeine so the drug is caffeine .

            There is some precaution that we should be aware by doing this experiment which is we cannot allow UV light to shine to anyone eyes , it can cause permanent eyes damage .While we are doing line on the TLC sheet we should use pencil instead of pen because it can contaminated our TLC paper.The solution point maybe moves with the pen ink.

Conclusion

            The R_f value was determined which is for reading 1 ,R_f for aspirin is 0.52 , upthamol is 0.46 , caffein is 0.22 and acetaminophen is  0.5 while for reading 2 ,  R_f value for aspirin is 0.55 , upthamol is 0.47 , caffein is 0.22 and acetaminophen is 0.47 .From the calculation the compound in the TLC tablet is caffeine.