Introduction Caffeine is a molecule that is similar to the purine base xanthine. The only recognizable difference is that caffeine has a methyl group. The goal of this experiment is to isolate caffeine from tea leaves, and then purify it by using sublimation. This experiment will use three techniques, extraction, recrystallization and melting point determination. A sequence of extractions has to be done to take out the other components from tea.
Poke a pencil through one of the loops you just made. Use the pencil to suspend the strip in a small glass or container. 5. Carefully add water to the glass until it reaches the bottom of the paper strip just below the ink dot. Be sure the ink stays above the water and the paper stays in the water.
Isolation of Caffeine from Tea CHEM243A 2-23-11 Abstract: The purpose of this experiment was to isolate caffeine from a tea bag. Once isolated, the caffeine was purified using sublimation. The percent recovery was calculated to be 83.3%. The melting point of the original substance was 51ºC-139ºC. Since it was inaccurate, the melting point of another group’s sample was recorded.
The extraction process is when a solvent, dichloromethane (15mL) is added to the filtrate in a separatory funnel; the mixture is gently swirled together 3 times, and stopcock is released in between to vent the funnel. Dichloromethane (including the emulsion) is then drained from the bottom into a 50mL Erlenmeyer flask. Same extraction process is repeated on the same filtrate and the dichloromethane is, once again, let out to the same 50mL Erlenmeyer flask as before. The combined dichloromethane solution and water (20mL) is poured into a rinsed separatory funnel. Mixture is gently swirled and drained out into an Erlenmeyer flask.
The chemical reaction for this experiment is: 3NaHCO3(aq) + C3H4OH(COOH)3(aq) C3H4OH(COONa)3(aq) + 3H2O(l) + 3CO2(g) sodium bicarbonate + citric acid sodium citrate + water + carbon dioxide Purpose: The purpose of this lab is to show visual evidence of the law of conservation of mass during a chemical reaction. Materials: 1) Plastic beaker 2) Paper towel 3) Effervescent tablet (Alka Seltzer) 4) Access to water 5) Balance 6) Safety goggles 7) Plastic bottle (500mL) with air-tight screw cap Variables: - Dependent Variables: - Independent Variables: Procedure: 1) Pour about 50 mL of water into the beaker. If you get the outside of the beaker wet, dry it using a paper towel. 2) Break the tablet in half. Shake or blow any loose grains off the tablet.
| 3 drops of 1% dimethylglyoxime solution. | [Ni(NH3)6]2+ + 2H2DMG→ Ni(HDMG)2 + 2NH4+ + 4NH3 | 9 Al3+ | By heating the solution in the hot water bath. | A black gelatinous precipitate was changed to colorless. | 6M NH3 | [Al(OH)4]- + 4H+ → Al3+ + 4H2O | 10 | Centrifuge the solution. | Colorless solution.
A wide choice of acid-base indicators is available, varying not only in the colours of the two forms but also in their sensitivity toward acid or base (Encyclopaedia Britannica, 2013). In relation to this practical the Sodium Hydroxide (NaOH) is the strong base which dissolves in water to form an alkaline solution. The concentration of this solution can be determined by titrating it with a standard solution of a strong acid such as Hydrochloric Acid (HCl). The indicator to be used is Methyl Orange. Apparatus: * * Pipette (10cm3) and Filler * Burette (50cm3) * Conical Flask * Funnel * Glass beaker * Stand and Clamp (for burette) * White paper * Chemicals (NaOH, HCl, Methyl Orange for indicator)
Aim: | The aim of this experiment is to analyse a sample of vinegar and determine it’s concentration. | | | Hypothesis: | It’s expected that the aceatic acid will have the concentration of 0.1mol as this is the molarity of the NaOH as they have a 1:1 ratio of moles as it states in their chemical equations. | | | Apparatus: | * 1 x retort stand * 1 x retort burette clamp * 1 x burette * 1 x pipette * 1 x glass funnel * 2 x Conical Flasks * Sheet of filter paper * 200mL of 0.1 mol L-1 NaOH * 200mL of acetic acid of unknown concentration | | | Procedure: | 1. WARNING: Wear safety glasses and gloves! 2.
Liquid resins are converted into insoluble and infusible solids through oxirane reactions. The oxirane structure is referred as epoxy functionality. The resin used in the experiment has a functionality of two. Resins are usually prepared with the reactions of bisphenols –and generally commercially bisphenol A- with epichlorohydrin or glycidyl chloride. Epoxy resins are generally cured with primary/secondary polyamines, anhydrides, and polyamides.
Three tests will then be performed to examine the identity and purity of the synthesized aspirin. The first test will detect the presence of leftover salicylic acid in the synthesized aspirin. The second test uses melting point to evaluate the purity of the aspirin product. A compound that contains impurities will tend to melt over a range of temperatures and at temperatures lower than the fixed mp for the pure compound. The third test will utilize thin layer chromatography to evaluate the purity of the aspirin as well as testing for the presence of leftover salicylic acid or other by products of the reactions.