Практикалық сабақтарының тақырыптары мен мазмұны Practical assignment №1
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chemistry (1)
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RENDERING AND ANNOTATION CHECKLIST UNIT 4. CHEMICAL Laboratory equipment STARTING UP READING Read and translate the text Laboratory equipment A) All the laboratories of inorganic chemistry are almost alike. These are large rooms where both students and research-workers carry out their experimental work. Modern laboratories of inorganic as well as organic and analytical chemistry are provided with gas and running water. Every laboratory is to be provided with a ventilating hood for the escape of both harmful and unpleasant vapours and odours. Every laboratory has to be lit up very well. There are many laboratory benches with a great number of drawers in every laboratory. Different apparatus devices as well as materials are to be kept in them. Besides we can see many shelves and cases for containers with chemicals. On every laboratory bench one can see test-tubes, flasks, beakers, funnels, evaporating dishes, weighing bottles. All this glassware should be kept in good order. Various burners serve for producing flames. Bunsen burner is to be mentioned among them. Different crucibles are to be employed when heating of solution and igniting of materials are to be carried out. Crucibles are usually made of quartz, porcelain and iron. In addition to these crucibles, there are platinum crucibles in some laboratories, but they are used very seldom. B) Every laboratory should be equipped with different kinds of apparatus. Everything in the laboratory is to have its definite place. Experiments in the Laboratory Many experiments can be carried out in the laboratoryof inorganic chemistry. Thus, if we want to obtain hydrogen chloride (HCL) which is often referred to as a hydrochloric acid gas, it is necessary to pour some sulphuric acid through a tube over the crystal of sodium chloride, in a flask. The fiask is to be heated. On warming the fiask, the hydrogen chloride is expelled as a colourless gas with a suffocating odour. It produces heavy clouds of white fumes when it comes in contact with the moist air of the room. It is soluble and it cannot be collected over water as are oxygen and hydrogen. It is much heavier than the air and may be passed through a glass tube to the bottle. If we dissolve some of the gas in water, the solution has a sour taste, reddens blue litmus, reacts with zinc, etc.: it is hydrochloric acid. When all the sodium chloride originally present in the flask has been transformed, the reaction is complete. The flask then contains a salt called sodium acid sulphate (NaHSO4) together, with unchanged excess of sulphuric acid. Nitric acid may be prepared by the reaction of concentrated sulphuric acid with sodium nitrate. In the laboratory method, a mixture of sodium nitrate and concentrated sulphuric acid is heated in a glass retort. Nitric acid is boiled out of the mixture and is condensed: NaNO3 + H2SO4 = HNO3+ NaHSO4 жүктеу/скачать 64,23 Kb. Достарыңызбен бөлісу:
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