Item no.: P3101100 Principle Unlike the other alkali-organyls, lithium organyls – with the exception of methyllithium – show a stronger covalent behaviour. They dissolve rather well in organic solvents, such as diethyl ether, tetrahydrofuran, and alkanes, and they are relatively stable in these solvents. Wurtz synthesis was developed in 1854 for the preparation of higher
Item no.: P3101000 Principle Haloalkanes react with magnesium to the so-called Grignard reagents in accordance with the general formula RMgX. With X = bromide or iodide, the reaction works best. Chlorides are usually more inert and require higher temperatures and longer reaction times for the conversion. The compounds that were discovered by Victor Grignard probably
Item no.: P3061861 Principle If the oxidation and reduction steps of an electrode reaction are rapid (high exchange current densities) then the passage of charge across the electrode-solution interface will barely displace the reaction equilibrium. Such an electrode is said to be non-polarisable in the sense that its potential, for small currents, is stable and
Item no.: P3020461 Principle The vaporisation of a liquid occurs with heat absorption. To determine the enthalpy of vaporisation, a known mass of the liquid which is to be investigated is vaporised in a special vaporisation vessel in a current of air. The quantity of heat absorbed, which corresponds to the enthalpy of vaporisation, can
Item no.: P2140400 Principle Due to internal friction among their particles, liquids and gases have different viscosities. The viscosity, a function of the substance’s structure and its temperature, can be experimentally determined, for example, by measuring the rate of fall of a ball in a tube filled with the liquid to be investigated. Tasks Measure
Item no.: P3010301 Principle Diffusion arises from the flow of matter down a concentration gradient. In the evaporation method, a stationary concentration gradient is achieved in which the concentration decreases linearly with distance. Under these conditions the diffusion coefficient of the diffusing substance may be calculated by a direct application of Fick’s first law of
Item no.: P2545001 Principle Various alloyed materials are subjected to polychromatic X-rays. The energy of the resulting fluorescence radiation is analysed with the aid of a semiconductor detector and a multichannel analyser. The energy of the corresponding characteristic X-ray fluorescence lines is determined. In order to determine the concentration of the alloy constituents, the intensity
Item no.: P3031760 Principle Chromatographic procedures allow a separation of substance mixtures with the aid of a stationary separation phase and a mobile phase. In gas chromatography the mobile phase is a gas. The mobile phase, to which the mixture to be separated is added, transports the substance mixture through the separation column at a
Item no.: P3111000 Principle In 1811, Avogadro stated his hypothesis that under the same conditions of pressure and temperature, equal volumes of all gases contain equal numbers of components (molecules, atoms). He derived this from the uniformity of the behaviour of (ideal) gases on increases in temperature and pressure (see the Gas Laws) and the
Item no.: P3030501 Principle A number of different mixtures of phenol and water are prepared and heated until complete miscibility is achieved. As the mixtures cool, two-phase systems form at certain temperatures which are recognisable by the appearance of turbidity. Plotting separation temperatures against compositions of the mixtures gives the separation curve. Tasks Plot the