Answer to Question #257627 in Molecular Physics | Thermodynamics for Jay

Question

A vacuum gauge reads 60.2 cm Hg. Determine the absolute pressure in kPa if the barometer reads 75.7 cm Hg.

Answer 1

$P_{vacuum \; gauge} = 60.2 \;cmHg \\ P_{atm} = 75.7 \;cmHg \\ P_{absolute} = -P_{vacuum \; gauge} + P_{atm} \\ = -60.2 + 75.7 \\ = 15.5 \; cmHg$

We know that 1 cm Hg = 1333.2 Pa

$P_{absolute} = 15.5 \times 1333.2 = 20664.6 \;Pa \\ P_{absolute} = 20.664 \;kPa$