The objectives of this experiment were to use qualitative schemes and basic solubility rules to determine the cationic composition of an unknown sample. Specifically, for this experiment, the unknown sample included some combination of Ag+, Pb2+, and Hg22+ cations.
When given a test tube of the unknown sample, four drops of 6 M HCl(aq) was first added in order to precipitate the ions into their respective chlorides, AgCl(s), Hg2Cl2(s), PbCl2(s), if present. After adding the HCl(aq) to the sample, the solution would turned milky white and a white precipitate settled to the bottom of the test tube, indicating that there was at least one of the ions initially present in the unknown solution. A large amount of HCl was not added because the AgCl(s) and PbCl2(s) would otherwise form soluble chloro complexes with the excess chloride atoms: PbCl42-(aq) and AgCl2-(aq). The solution was then centrifuged to fully separate the suspended chlorides from the liquid. An additional drop of HCl was then added to the
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However, after addition and centrifugation, there was no observable change, indicating that there were no Hg22+ cations initially present in the unknown sample. The supernatant, which now contained Ag(NH3)2+(aq), was then decanted into another test tube for further analysis. One unexpected result was that a white solid precipitate remained at the bottom of the tube. This was unexpected since if there were silver in the solution, it would have dissolved into Ag(NH3)2+(aq) after addition of ammonia. The mystery precipitate could have been either unreacted AgCl (s), PbCl2(s) that did not dissolve in the first separation step, or a newly formed compound. In order to determine this, the supernatant underwent the final identification
The purpose for this lab was to use aluminum from a soda can to form a chemical compound known as hydrated potassium aluminum sulfate. In the lab aluminum waste were dissolved in KOH or potassium sulfide to form a complex alum. The solution was then filtered through gravity filtration to remove any solid material. 25 mLs of sulfuric acid was then added while gently boiling the solution resulting in crystals forming after cooling in an ice bath. The product was then collected and filter through vacuum filtration. Lastly, crystals were collected and weighed on a scale.
The primary goal of this laboratory project was to identify an unknown compound and determine its chemical and physical properties. First the appearance, odor, solubility, and conductivity of the compound were observed and measured so that they could be compared to those of known compounds. Then the cation present in the compound was identified using the flame test. The identity of the anion present in the compound was deduced through a series of chemical tests (Cooper, 2009).
Thorough analysis of the graph displayed enough evidence suggesting that an increase in substrate concentration will increase the height of bubbles until it reaches the optimum amount of substrate concentration, resulting in a plateau in the graphs (figure 2). Hence; supported the hypothesis.
Firstly, an amount of 40.90 g of NaCl was weighed using electronic balance (Adventurer™, Ohaus) and later was placed in a 500 ml beaker. Then, 6.05 g of Tris base, followed by 10.00 g of CTAB and 3.70 g of EDTA were added into the beaker. After that, 400 ml of sterilized distilled water, sdH2O was poured into the beaker to dissolve the substances. Then, the solution was stirred using the magnetic stirrer until the solution become crystal clear for about 3 hours on a hotplate stirrer (Lab Tech® LMS-1003). After the solution become clear, it was cool down to room temperature. Later, the solution was poured into 500 ml sterilized bottle. The bottle then was fully wrapped with aluminium foil to avoid from light. Next, 1 mL of 2-mercaptoethanol-β-mercapto was added into fully covered bottle. Lastly, the volume of the solution in the bottle was added with sdH2O until it reaches 500 ml. The bottle was labelled accordingly and was stored on chemical working bench.
Table 1 provides the results from this experiment by showing which halides did react with the 1% ethanolic silver nitrate solution and which ones did not react. Through the evaluation of the precipitate, 2-chloro-2-methylpropane reacted instantly with the silver nitrate solution. This reaction occurred instantaneously due to the fact that SN1 reactions favor steric hindrance and the leaving group, chlorine, was a tertiary substrate. On the other hand, the two substrates that had secondary leaving groups were 2-chlorobutane and 2-bromobutane. When 2-bromobutane was mixed with the 1% ethanolic silver nitrate solution, the precipitate that was formed, progressively became cloudier after heating and cooling in a water bath. Although 2-chlorobutane was expected to react, the halide did not show any precipitate before or after heating and cooling. This alkyl halide did not react due to the fact that the leaving group is chlorine, which does not have a strong attraction to the silver nitrate solution. The
Cations are positively charged ions, which are attracted to their negatively charged counterparts, anions. Precipitates can form when these cations and anions combine in aqueous solutions; however, precipitates only form if one of the products of the chemical reaction is not soluble in that solution. Solubility is instrumental in understanding how precipitation reactions occur. This is because solubility rules, determine whether a precipitate can form. A precipitate can form if the cation in the compound is soluble when combined with an anion. For example when the solutions silver nitrate and sodium chloride (reactants) are mixed, silver chloride and sodium nitrate (products) are formed. Following the solubility laws, silver nitrate is the precipitate, as it isn’t
Prediction: Draw a sketch to show the shape of the curve you expect for the solubility of a typical solid dissolving in water at different temperatures. Plot solubility on the y-axis and temperature on the x-axis.
To undertake titration and colorimetry to determine the concentration of solutions By carrying out titrations and colorimetry, the aim of this investigations was to use these methods such that the concentrations of different solutions used can be identified, and to help find the concentration of the unknown solution that were given. Using Titration and colorimetry the concentrations of different solutions in general can be determined and this helps to identify solutions with unknown concentrations. In this assignment I was asked to carry out two different scientific techniques and find the concentration of different solutions.
Solid A was identified to be sodium chloride, solid B was identified to be sucrose, and Solid C was identified to be corn starch. Within the Information Chart – Mystery White Solid Lab there are results that distinguishes itself from the other 4 experimental results within each test. Such as: the high conductivity and high melting point of sodium chloride, and the iodine reaction of corn starch. Solid A is an ionic compound due to its high melting point and high electrical conductivity (7), within the Information Chart – Mystery White Solid Lab there is only one ionic compound which is sodium chloride, with the test results of Solid A, it can be concluded that is a sodium chloride. Solid B was identified as sucrose due to its low electrical
However, there is no color change at end point of these reactions, so an indicator had to be added into the solutions to indicate the end point. An indicator is a chemical which is used to indicate the presence of the another substance in the solution; it changes colors when the ions H+ are added or removed by dissociation reaction. In this experiment, phenolphthalein was used as an indicator to indicate the presence of base in a solution by changing the color of the solution from colorless into pink. When the concentration of H+ is low, the solution becomes pink, and when the concentration of ions H+ is high, it becomes clear. The equivalent point is determined when there is a color change from colorless into light pink, and it is also an approximation of the end point. The concentrations were calculated by the equation M1V1 = M2V2, which means that the moles number of the base must equal to the moles number of an acid. The mole ratio in these reactions are 1:1 that means the moles’ number of the first reactant is equal to the moles’ number of the second one at the end
The ability to analyze a substance and determine properties of the substance is an important skill for AP Chemistry students. Major concepts for the “Analysis of Alum” laboratory are percent composition, water of hydration, and molecular formula. They will be used in three different experiments to determine the melting point of alum, the mole ratio of hydrated water to anhydrous alum, and percent of sulfate ion contained in alum. The values acquired in the lab should be close to the calculated values of 92.5 ˚F, 12 moles of water to 1 mole of alum, and 59%, respectively.
The procedure for this experiment can be found in Inorganic Chemistry Lab Manual prepared by Dr. Virgil Payne.
In our experiment we utilized the hydrate cobaltous chloride. Hydrates are crystalline compounds in which one or more molecules of water are combined with each unit of a salt. Cobalt (II) chloride hexahydrate is an inorganic compound which is a deep rose color in its hydrated form. As an inducer of
Compared to the 0.5 M hydrochloric acid that was less concentrated, the more concentrated 2 M hydrochloric acid c...
The sample was subjected to steam distillation as illustrated in Figure 1. A total of 50ml of distillate was collected while recording the temperature for every 5.0 ml of distillate. The distillate was transferred into a 250ml Erlenmeyer flask and 3.0 g of NaCl was added. The flask was cooled and the content was transferred into a 250-ml separatory funnel. Then 25.0ml of hexane was added and the mixture was shaken for 5 minutes with occasional venting. The aqueous layer was discarded and the organic layer was left inside. About 25.0ml of 10% NaOH was then added and the mixture was shaken as before. The aqueous layer was collected and then cooled in an ice bath. It was then acidified with enough 6.00 M HCl while the pH is being monitored with red litmus paper. Another 25.0 ml of hexane was added and the mixture was shaken as before. The hexane extract was saved and a small amount of anhydrous sodium sulfate was added. The mixture was then swirled for a couple of minutes then filtered. A small amount of the final extracted was tested separately with 1% FeCl3 and Bayer’s reagent.