- •Experiments
- •In the Laboratory
- •1. Handling the Bunsen burner
- •2. Handling chemical reagents
- •3. Handling glassware
- •4. Heating procedure
- •Seminar 1 chemical equivalent. Law of equivalents
- •Questions and problems
- •Seminar 2 rate of a chemical reaction. Chemical equilibrium
- •Questions and problems
- •Experiment 1
- •Ionic equilibrium
- •1. Dissociation of weak electrolytes
- •1. Formation and dissolution of a precipitate
- •2. Direction of a chemical reaction
- •3. Heterogenous equilibrium
- •Questions and problems
- •Experiment 3
- •Ionic product of water. Ph. Hydrolysis of salts
- •1. Determination of pH of solutions of some salts
- •Experiment 4 oxidation-reduction reactions
- •Concentrated sulfuric acid
- •Experiment 5 complex (coordinate) compounds
- •1. Formation of complex compounds
- •2. Destruction of complex compounds
- •4. Dissociation of complex compounds
- •Questions and problems
- •Experiment 6
- •(Alkaline and alkaline earth metals)
- •Biological significance of alkaline metals
- •Biological and agricultural properties of elements of
- •Iia group
- •1. Interaction of sodium with air and water
- •Experiment 7 elements of iiia and iva groups
- •Biological properties of boron and aluminum
- •1. Properties of boric acid and its salts
- •Experiment 8 elements of va and via groups
- •Biological importance of sulfur
- •1. Formation and properties of ammonia
- •2. Oxidizing properties of nitric acid
Biological significance of alkaline metals
Lithium is found in the liver and lungs of animals. Large concentrations of lithium are dangerous for humans . Particles of dust and smoke containing lithium provoke malignant tumors. Sodium as NaCl is necessary for the balance of salt exchange in organisms, sodium bicarbonate is used to lower the acidity of gastric juice. In living organisms potassium is situated in liver, spleen, it regulates the function of muscle cells and nervous systems. Rubidium is found in the leaves of plants (beetroot, sugar-cane, tabacoo, tea, coffee, cocoa). In animal organisms it is localized in muscles performing large load - heart muscle and pectoral muscles of birds. Cesium is found in mineral water, plants and living organisms. Compounds of rubidium and cesium are necessary for the growth of plants.
Alkaline earth metals Ca, Sr, Ba, Ra are situated in the IIA group of the periodic table. Atoms of these elements have two valence electrons. While losing them, atoms of alkaline earth elements transfer into positively charged ions and gain the oxidation number +2.
The presence of non-filled sublevels (d- and f-) makes Ca, Sr, Ba and Ra more chemically active and having physical properties rather different than those of Be and Mg.
Metals of IIA group are less active than alkaline metals. The growth of the atomic radius, lowering of the ionization potential and of the electronegativity define the growth of their chemical activity with increase of charges of the nuclei.
In the air alkaline earth metals easily form oxides. They replace hydrogen both from water and from acids:
M +2HCl = MCl2 + H2
M + 2H2O = M(OH)2 + H2
The basic character of oxides and hydroxides increases with the increase of atomic radii from calcium to radium.
Alkaline earth metals form different sparingly soluble salts: carbonates, phosphates, chromates, sulfates. The solubility of sulfates lowers from calcium to radium.
Natural water containing soluble salts of calcium and magnum is called hard water. The presence of hydrocarbonates of calcium and magnum stipulates the temporary hardness of water. Chlorides and sulfates of these elements cause the constant hardness. The sum of temporary and constant hardness gives the overall hardness of water.
Biological and agricultural properties of elements of
Iia group
Beryllium and its compounds are toxic. The beryllium-poisoning may cause the death.
Magnum compounds can be found in algae, fungi, ferns, in the tissues of animals. Magnum is a complexing ion in chlorophyll.
Calcium is a constituent of the bones of vertebrates, predominantly as ortophosphate Ca3(PO4)2. Egg-shells, tests of sea animals, shells mainly consist of calcium carbonate. Organic salts of calcium play a significant role in metabolism of plants. The deficiency in calcium leads to stopping of their growth, development of rhizomes, the leaves cover by brown spots and die off. The animals suffer from rachitis, the heart activity decreases, the blood coagulability becomes worse.
Calcium ions enter human organisms with milk and meat meals while magnum ions - with vegetable meal.
Strontium compounds in human organisms are mainly concentrated in bones, the excess (more than 10-3 %) leads to their fragile.
There are approximately 100 times less barium compounds in human bodies than those of strontium. In very small quantities barium compounds stimulate activity of marrow. In large quantities they are very toxic and provoke weakness, gastric-intestinal diseases, brain disorders. Barium chloride and carbonate are used in the agriculture as chemical weed-killers and pest-killers.
EXPERIMENTAL PART