Item no.: P4120160 Principle Amino acid molecules carry both acid and amino groups. They can therefore form both acidic anions and basic cations. The pH at which these two types of iones are both present in the same concentration is called the isoelectric point. Tasks This isoelectric point is to be determined by recording the
Item no.: P3031660 Principle In countercurrent distillation (rectification) using a column, the rising vapour can enter into interactions with the condensate. In this manner, a fractional distillation, i.e. a distillation in several steps for the separation of substances with similar boiling points, can be performed in a single apparatus. If bubble tray columns are used
Item no.: P3110200 Principle The Haber-Bosch process was the first large-scale technical method for producing nitrogen compounds based on the nitrogen in the air. The formation of ammonia benefits from a falling temperature and rising pressure since it is an exothermic reaction that is accompanied by a decrease in volume. At room temperature, however, the
Item no.: P3031501 Principle The separation power of a rectification (fractionating) column can be determined using an appropriate binary mixture whose equilibrium composition is measured in the distillation flask and in the domed glass head of the distillation apparatus. The number of theoretical trays can be numerically or graphically obtained from the measured values. Tasks
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