Water will act as initial solvent for caffeine extraction. This is due to water that slowly soluble with caffeine at ambient temperature but highly soluble when temperature is at 100°C. Then, methylene chloride is chosen as the extraction solvent, due to its miscibility with caffeine and immiscibility with water. As mentioned above, the immiscible pair is chose for the extraction part because to allow the aqueous and organic layers to be separated. Basically, the bottom layer is the aqueous layer while the upper layer is the organic compound.
The goal of the experiment is to synthesize a bromohexane compound from 1-hexene and HBr(aq) under reflux conditions and use the silver nitrate and sodium iodide tests to determine if the product is a primary or secondary hydrocarbon. The heterogeneous reaction mixture contains 1-hexene, 48% HBr(aq), and tetrabutylammonium bromide and was heated to under reflux conditions. Heating under reflux means that the reaction mixture is heated at its boiling point so that the reaction can proceed at a faster rate. The attached reflux condenser allows volatile substances to return to the reaction flask so that no material is lost. Since alkenes are immiscible with concentrated HBr, tetrabutylammonium bromide is used as a phase-transfer catalyst.
The average equivalent mass for the acid is 135g/mol H+. 3. The answer obtained in Question #2 is the equivalent mass of the acid rather than the molar mass because the acid could be polyprotic, which would mean the equivalent mass is different from the molar mass since it is depending on moles of H+ per molecule, and there could be multiple moles of H+ ions in one mole of a molecule. 4. The KHP and the acid samples must be dried, because there would still be extra water which would skew the molarity.
In this experiment, the dark blue colour is visible because of the helical amylose and amylopectin reacting with iodine (Travers et al., 2002). The starch-iodide complex forms because of the transfer of charge between the starch and iodide ion and results in spacing between the energy levels. This allows the complex to absorb light at different wavelengths resulting in a dark blue colour (Travers et al., 2002). A blue colour would indicate a positive test while a yellow colour would show a negative test. The Benedict’s test is useful for reducing sugars.
1) Percentage yield experiment: First we measured 20cm3 of sulphuric acid into a beaker using a measuring cylinder, this will help us determine the percentage yield at the end of the experiment. We then heated the beaker containing the sulphuric acid using a Bunsen burner in order to heat it up for the copper oxide to mix with. We then weighed out 1.02g of copper oxide and added it to the acid and stirred it whilst doing so, we did that until the liquid turned blue, this proves that the chemicals have mixed together. We then weighed this liquid which will help us determine the percentage yield. We then filtered the liquid off which gave us the amount we obtained.
The active ingredients in the alka seltzer tablet are “As the tablets dissolve, the sodium bicarbonate splits apart to form sodium and bicarbonate ions. The bicarbonate ions react with hydrogen ions from the citric acid to form carbon dioxide gas (and water). This is how the bubbles are made.”(Scientific American) These bubbles are representative of a chemical change and the resulting carbon dioxide should increase the water 's density. This may actually increase the volume of the water taking longer to boil, this difference may be minuscule, even negligible, but there 's a possibility for distinct change in results. This scientific American puts it best “For the reaction to occur,
In addition, phenolphthalein was added as an indicator. The aliquots were titrated against sodium hydroxide (NaOH) solution until end point was reached, after which volume of NaOH consumed was recorded. The value of the rate constant, k, obtained was 0.0002 s-1. The experiment was then repeated with 40/60 V/V isopropanol/water mixture and a larger value of k = 0.0007 s-1 was obtained. We concluded that the rate of hydrolysis of (CH3)3CCl is directly proportional to water content in the solvent mixture.
Due to water’s polar structure, ions in some compounds attract and form bonds with water molecules, forming hydrates. A hydrate is a salt that has water molecules trapped within its crystals. Every hydrate has a certain number of water molecules weakly bonded to the salt as follows: salt • number of water molecules Anhydrous salts are salts that can form hydrates but which have had all the water driven off, usually by heat. By heating the Copper (II) sulphate hydrate until its color changes from blue to white, the compound can be decomposed into CuSO4, a white crystal, and H2O gas, represented as follows: CuSO4 • xH2O(s) ←⎯→ CuSO4(s) + xH2O(g) Because of the mass conservation law and the fixed proportion of water molecules, the mole of H2O can be calculated by calculating the mass difference of the substance before and after the reaction: Mole of H2O = (Mass of substance before the reaction) (Mass
When tin chloride is added to the solution, Sn2+ took away positive charged ions; Fe3+ to Fe2+ (2Fe3+(aq) + Sn2+(aq) → 2Fe2+(aq) + Sn4+(aq)). This took away Fe3+ from the solution, causing the equilibrium to change to the reactants to balance the concentration of Fe2+. The solution turned a lighter color to increased rate of the reverse reaction. When AgNO3 was added to the solution, the silver nitrate broke down into Ag+ and
A spectrophotometer is used to read the absorbance value of the cations in a flame that emits a photon read by the machine. Different elements will emit different lengths of photons which in turn produces an absorbance value. The absorbance values are then plotted on a calibration graph to determine the unknown concentration. EDTA titrations require much less equipment since it is more of a chemical test. An indicator EBT is added to a known volume of your water sample and should turn blue.