Question

Convert the following readings of pressure to kPa assuming that barometer reads 760 mm of Hg. (i) 80 cm of Hg (ii) 30 cm Hg vacuum (iii) 1.35 m H2O gauge (iv) 4.2 bar.

Answer 1

The converted measurements are: (i) 80 cm of Hg = 106.4 kPa, (ii) 30 cm Hg vacuum = 61.18 kPa, (iii) 1.35 m H2O gauge = 179.55 kPa, (iv) 4.2 bar = 420 kPa.

Step-by-step explanation:

The correct answer is option B. To convert the given readings of pressure to kPa, we need to use the conversion factors from the equivalent pressure units. The conversion factors are:

• 1 atm = 101.3 kPa
• 1 mm Hg = 0.133 kPa
• 1 torr = 0.133 kPa

(i) 80 cm of Hg: 80 cm Hg = 800 mm Hg (1 cm Hg = 10 mm Hg). 800 mm Hg * 0.133 kPa/mm Hg = 106.4 kPa.

(ii) 30 cm Hg vacuum: 30 cm Hg = 300 mm Hg. Since it is a vacuum, we subtract it from atmospheric pressure. 760 mm Hg - 300 mm Hg = 460 mm Hg. 460 mm Hg * 0.133 kPa/mm Hg = 61.18 kPa.

(iii) 1.35 m H2O gauge: 1.35 m H2O * 100 cm/m * 10 mm/cm = 1350 mm H2O. 1350 mm H2O * 0.133 kPa/mm H2O = 179.55 kPa.

(iv) 4.2 bar: 4.2 bar * 100 kPa/bar = 420 kPa.

Therefore, the converted measurements to kPa are:
(i) 80 cm of Hg = 106.4 kPa
(ii) 30 cm Hg vacuum = 61.18 kPa
(iii) 1.35 m H2O gauge = 179.55 kPa
(iv) 4.2 bar = 420 kPa.