The surface tension of water was determined in a laboratory by using the drop weight method. 100 drops were released from a burette the inne

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The surface tension of water was determined in a laboratory by using the drop weight method. 100 drops were released from a burette the inner diameter of whose opening is 1.8 mm

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Ladonna 4 years 2021-09-04T09:36:32+00:00 1 Answers 82 views 0

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  1. Doris
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    2021-09-04T09:38:18+00:00
    Reply

    Answer:

    0.06563 N/m

    The percentage difference between the calculated and tabulated value of water surface tension is 9.78%

    Explanation:

    Solution:-

    – Surface tension is the ability of any fluid to resist any external force due to cohesive nature of the fluid molecules.

    – Surface tension ( γ ) is defined as the force imparted per unit length on the fluid.

                              γ = F / L

    Where,

                 F: Force

                 L: The length over which force is felt

    – The mass ( M = 3.78g ) of ( n = 100 ) water droplets are carefully burette. We need to determine the mass of a single droplet as follows:

                            m = M / n

                            m = 3.78 / 100

                            m = 0.0378 g        

    – Assuming the distance over which the drop falls is negligible and resistive forces are negligible. Then the only force acting on the droplet is due to gravity ( Weight of the droplet ):

                           F = m*g

                           F = 0.0378*9.81*10^-3

                           F = 0.000370818 N      

    – The length over which the force is felt can be modeled into a circular patch with diameter ( d ) = equal to the diameter ( d ) of the single water drop. The length ( L ) is defined as the circumference of the patch:

                           L = π*d

                           L = π*( 0.0018 )

                           L = 0.00565 m

    – The surface tension would be:

                           γ = F / L

                           γ = 0.000370818 / 0.00565

                           γ = 0.06563 N / m

    – The given value of water’s surface tension is given as follows:

                          γa = 0.07275 N/m

    – To compare the two values we will determine the percentage difference between the value evaluated  and tabulated value as follows:

                       % diff = \frac{0.07275- 0.06563}{0.07275} * 100 \\\\diff = 9.78 \\\\

    – The percentage difference ( 9.78% ) between the two values is within  practical limits of 10%. Hence, the calculated can be accepted.

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