Water rises in a capillary tube to a height of 4.8 cm at 25°C. The density of water at 25°C is 0.9984 g/cc. The same capillary, when filled with mercury, contained 40.5 g/cm of the capillary. Calculate the surface tension of water. Density of Hg = 13.6 g/cc and g = 981 cm s^(-2)

Water rises in a capillary tube to a height of 4.8 cm at 25°C. The de

1.	Water rises in a capillary tube to a height of 4.8 cm at 25°C. The density of water at 25°C is 0.9984 g/cc. The same capillary, when filled with mercury, contained 40.5 g/cm of the capillary. Calculate the surface tension of water. Density of Hg = 13.6 g/cc and g = 981 cm s^(-2)
Answer» Solution : Let US first calculate the radius of the capillary tube (R). Wt. of Hg in the capillary = mass of `Hg xx G` `w_(Hg) ="Volume" xx "density" xx g` `w_(Hg) = pir^(2)H xx d xx g` or `(w_(Hg))/h = pir^(2)dg = 40.5 g//cm` `therefore r= sqrt((40.5)/((22//7) xx 13.6 xx 981)) = 0.031 cm` We have, `Y_(H_(2)O) = (hdrg)/2` `=(4.8 xx 0.9984 xx 0.031 xx 981)/2` `=72.86 "DYNE" cm^(-1)`