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Standard VIII

Chemistry

Surface Tension

When a capill...

Question

When a capillary tube is immersed in ethyl alcohol whose surface tension is $20 d y n e c m^{- 1}$ ,the liquid rises to a height of $10 c m$ . Density of the liquid is $0.8 g - c m^{- 3}$ . If $g = 10 m s^{- 2}$ , the radius of the capillary tube is $. . . . . . m m .$ (Angle of contact of ethyl alcohol w.r.t. glass is $60^{o}$ ).

0.0025

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0.025

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0.25

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2.5

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Solution

The correct option is A $0.025$
$T = 20 d y n e / c m$
$= 0.02 N / m$
By using formula for radius, $r = \frac{2 T c o s θ}{h ρ g}$
$r = \frac{2 \times 0.02 \times cos 60}{0.1 \times 1000 \times 10}$
$= 0.02 m m$

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The surface tension of a liquid is 80 dyne/cm. Its relative density is 0.8. If the angle of contact between the liquid and glass is $60^{\circ}$ , find the height to which the liquid rises in a glass capillary tube of radius 1 mm. $(g = 10 m / s^{2})$

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When a capillary tube is immersed in ethyl alcohol whose surface tension is 20 dyne cm−1,the liquid rises to a height of 10cm. Density of the liquid is 0.8 g−cm−3. If g=10ms−2, the radius of the capillary tube is ......mm. (Angle of contact of ethyl alcohol w.r.t. glass is 60o).

The correct option is A 0.025T=20 dyne/cm =0.02N/mBy using formula for radius, r=2Tcosθhρgr=2×0.02×cos600.1×1000×10 =0.02mm

The correct option is A $0.025$
$T = 20 d y n e / c m$
$= 0.02 N / m$
By using formula for radius, $r = \frac{2 T c o s θ}{h ρ g}$
$r = \frac{2 \times 0.02 \times cos 60}{0.1 \times 1000 \times 10}$
$= 0.02 m m$