Question

You obtain a mercury barometric reading of 760 mm Hg at 17°C. Using the following factor table, compute the corrected pressure.

° C	740	750	760
17	2.17	2.20	2.23
18	2.29	2.32	2.35
19	2.38	2.41	2.44

a.	223.0 mm Hg
b.	747.7 mm Hg
c.	757.8 mm Hg
d.	762.3 mm Hg

Answer 1

The expansion of mercury takes place when the temperature increases in the barometer. Since the barometer is calibrated for 0^oC therefore, a correction must be applied to compensate for the expansion of the mercury for higher temperatures. The table given in the problem above shows the correction, in millimeters (mm), which needs to be subtracted from the reading of atmospheric pressure.

Barometer reading at 17^oC = 760 mmHg

Correction from the table = 2.23

Therefore, corrected pressure = 760 - 2.23

= 757.8 mmHg