Question

Mercury has an angle of contact equal to 140° with soda lime glass. A narrow tube of radius 1.00 mm made of this glass is dipped in a trough containing mercury. By what amount does the mercury dip down in the tube relative to the liquid surface outside? Surface tension of mercury at the temperature of the experiment is 0.465 N m–1. Density of mercury = 13.6 × 103 kg m–3.

Answer 1

Here,
angle of contact ( ∅) = 140°
Radius of tube ( r) = 1mm = 10^-3 m
Surface tension ( S) = 0.465 N/m
density of mercury ( d) = 13.6 × 10³ kg/m³

Height of liquid rise or fall due to surface tension ( h) = 2Scos∅/rdg
= 2×0.465 × cos140°/10^-3 × 13.6×10³×9.8
= 2 × 0.465 × (-0.766)/13.6 × 9.8
= -5.34 × 10^-3 m or -5.34 mm

Hence, mercury level depressed by 5.34 mm