Barometer reading

For records on weather maps, meteoroiogists customariiy correct barometer readings to sea ievei, and some barometers may be caiibrated accordingiy. Such instruments are not suitabie for iaboratory use where true pressure under standard conditions is required. Scaie corrections shouid be specified in the maker s instructions with the instrument, and are aiso indicated by the iack of correspondence between a gauge mark usuaiiy piaced exactiy 76.2 cm from the zero point and the 76.2-cm scaie graduation. 

The mercury barometer (Fig. 10-11) indicates directly the absolute pressure of the atmosphere in terms of height of the mercuiy column. Normal (standard) barometric pressure is 101.325 kPa by definition. Equivalents of this pressure in other units are 760 mm mercury (at 0°C), 29.921 iuHg (at 0°C), 14.696 IbFin, and 1 atm. For cases in which barometer readings, when expressed by the height of a mercuiy column, must be corrected to standard temperature (usually 0°C), appropriate temperature correction factors are given in ASME PTC, op. cit., pp. 23-26 and Weast, Handbook of Chemistty and Physics, 59th ed., Chemical Rubber, Cleveland, 1978-1979, pp. E39-E41. 

B = minimum barometric pressure (mbar) (use 0.94 of mean barometer reading),... 

If a barometer were filled with a liquid of density 1.60 g/ml, what would be the reading when the mercury barometer read 730 torr The density of mercury is 13.56 g/ml. 

A mercury barometer reading of 728.3 mm is obtained at 23°C with a brass scale. What is the barometer reading "corrected to 0°C"—that is, in torr ... 

What is the atmospheric pressure in lbs/in- when the barometer reading is 720 torr ... 

A quantity of gas is collected in a graduated tube over mercury. The volume of gas at 20°C is 50.0 cm3, and the level of the mercury in the tube is 200 mm above the outside mercury level (see Fig. 5-7). The barometer reads 750 torr. Find the volume at S.T.P. The vapor pressure of mercury is not significant at this... 

A volume of 95 cm3 of nitrous oxide at 27°C is collected over mercury in a graduated tube. The level of mercury inside the tube is 60 mm above the outside level when the barometer reads 750 torr. (a) Calculate the volume of the gas at S.T.P. (b) What volume would the gas occupy at 40°C with a barometric pressure of 745 torr and the mercury level... 

If temperature does not change with height, estimate the boiling point of water at a height of 3000 m above sea-level. The barometer reading at sea-level is 98.4 kN/m2 and the temperature is 288.7 K. The vapour pressure of water at 288.7 K is 1.77 kN/m2. The effective molecular weight of air is 29 kg/kmol. 

What is the pressure contribution of C02 to the atmospheric pressure on a very dry day when the barometer read 0.98 atm Convert your answer into three different units. 

The barometer reads 740 mm Hg. Calculate tank pressure in psia. 

Whatever style of notebook is used, the principle is the same Record all data directly in your notebook. Data may be copied into tlie notebook from a partner s notebook in those cases where it is clearly impossible for both partners to record data at the same time. Even then, a carbon copy or a photocopy of the original pages is better, since it avoids copying errors and saves time. In particular, do not use odd scraps of paper to record such incidental data as weights, barometer readings, and temperatures with the idea of copying them into the notebook at a later time. If anything must be copied from another source (calibration chart, reference book, etc.), identify it with an appropriate reference. 

Remove the stopper entirely (a distance of 2 or 3 in.) from the carboy, and replace it in the shortest possible time, making sure that it is tight. As the gas warms back up to the bath temperature, the pressure will increase and finally (in about 15 min) reach a new constant value ps, which can be determined from the manometer reading and the barometer reading. At some point in the procedure, a barometer reading p should be taken as well as a bath-temperature reading. 

The entries A in the table below are calculated from Eq. (XVlll-1) on the assumption that the barometer has a brass scale graduated to be accurate at 0°C. See Chapter XIX for a description of the recommended procedure for reading a barometer. These corrections should be subtracted from the observed barometer readings i.e., p(Torr) = PobsCnun, 7) — A. (If the brass scale is accurate at 20°C, the appropriate corrections are approximately 0.3 mm greater than those given.) Once the barometer reading has been corrected to 0°C, the pressure is referred to as Torr rather than mm Hg. 

If the barometer reads 751 mm Hg, what are the partial pressures of oxygen and nitrogen in the atmosphere ... 

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