Then you will fill a BURETTE with sodium hydroxide (a base) that has a known concentration. Because all the reactants and products in this reaction are colourless, an INDICATOR DYE is added to the sulphuric acid to let us know when all the acid present has been EXACTLY NEUTRALIZED by adding base. Finally, the sodium hydroxide in the burette is added to the acid/indicator solution until the indicator changes colour. (An indicator dye is a chemical that has a different colour in an acid and a base.) PROCEDURE 1.
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.
6. Wash, dry and observe under oil immersion lens. Differential stains render one type of microbe one colour and other types of microbes another colour. In the Gram stain, Gram positive organisms retain the primary dye complex (crystal violet-iodine) whereas Gram negative cells loose the primary dye complex during the challenge rinse. Most differential stains have a challenge step that follows staining with a primary dye.
This step is slightly different from brewing tea because only 10 mL of water is used. All of the water immediately absorbs into the bag and must be squeezed out. Brewing tea to drink requires much more water. The next step in isolation is to add dichloromethane. The purpose of this step is to separate the aqueous layer from the organic layer.
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)
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.
This standardized solution of sodium hydroxide can then be used to determine the concentration of acid in the sample of gastric juice. Acid-base titration is when a titration is carried out with a known volume of a strong acid which in this case is HCl, of unknown concentration, with a standard solution of a strong base NaOH. The reaction taking place is: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(aq) A titration can be used to find the concentration of an acid in gastric juices because the acidity in the gastric juices is mainly caused by hydrochloric
Oil of vitriol, also known as sulfuric acid .Sulfuric acid? What is it? Sulfuric acid is a highly corrosive strong mineral acid with the molecular formula of H2 SO4. It's a colorless or slightly yellow liquid which is soluble in water at all concentrations. Sometimes, it could be dark brown by being dyed during its industrial production process in order to alert people to its hazards.
Dipole-dipole forces are permanent dipoles due to different electronegativity. Hydrogen bonding is a strong dipole that forms when H bonds to N, O, or F. [7] Nitric acid (HNO3) is a colorless, toxic, oxidizing, and corrosive liquid commonly used as laboratory reagent and for the manufacture of fertilizers and explosives. [8] It is completely miscible and has a dipole moment of 2.17D[2]. It contains one hydrogen bond and is a polar molecule. Water (H2O) is colorless liquid that’s the basis of life on Earth.
Thin Layer Chromatography Introduction (Adapted from Mohrig, 1st ed., pp. 151-162.) Chromatography is a sophisticated method of separating mixtures of two or more compounds. The separation is accomplished by the distribution of the mixture between two phases: one that is stationary and one that is moving. Chromatography works on the principle that different compounds will have different solubilities and adsorption to the two phases between which they are to be partitioned.