SURFACE TENSION BY THE RING METHOD

SURFACE TENSION BY THE RING METHOD - T (c) F (mN) St (mN/m)...

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SURFACE TENSION BY THE RING METHOD * Objective: 1. Measuring the surface tension (St) for Ethylene Glycol. 2. Determining Temperature Coefficient (Tc). 3. Determining the Total Surface Energy per unit area (Ua). * Theory: Intermolecular forces in liquids are very large not like those of the gases. So, at the liquid gas phase there exists a net force that points to the liquid phase. * Experiment: Refer to the book pages 81-86 Data: (GLYCE ROL, Dia = F(mN) T(C) T(K) F(mN) T(C) T(K) 8.1 22.5 295.65 7.1 23 296.15 8.1 34 307.15 6.97 33 306.15 8.1 44 317.15 6.91 43 316.15 8 54 327.15 6.65 53 326.15 8 63.5 336.65 6.8 63 336.15 7.8 73.5 346.65 * Calculations:- * for GLYCEROL , r = 0.94cm * Using Formula 4: St = F / (4)(3.14)(r) -------------- 4 Values of Surface tension (St) : At 22.5 C : (8.1/1000) / (4)(3.14)(0.94/100) = 0.0686 N The rest of the values are tabulated as follows:
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Unformatted text preview: T (c) F (mN) St (mN/m) 20.5 6.12 25.9 35.0 6.08 25.7 45.5 6.05 25.6 54.5 5.97 25.3 64.8 5.80 24.6 74.0 5.68 24.1 y = -26.121x + 707.3 10 20 30 40 50 60 70 80 90 24 24.5 25 25.5 26 St Vs T From the graph equation: • The slope = dSt / dT = -26.121 • Ua = St – T.dSt / dT at 20.5 C Ua = 25.9 – (25).(-26.121) = 678.9 J/m • Temperature Coefficient Tc is given by Formula (6): Tc = St . (V m ) 2/3 = 1.9 X 10-7 J/K The nearly constant value = 2.1 X 10-7 J/K The difference = (1.9 X 10-7- 2.1 X 10-7 ) / 1.9 X 10-7 = 10.5 % This percentage of error could have occurred due to non-perfect performance of the experiment. * References: “PHYWE, University Laboratory Experiments CHEMISTRY”, P 3.2.4....
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This note was uploaded on 04/13/2011 for the course CHEM 311 taught by Professor Alial-habib during the Fall '09 term at King Fahd University of Petroleum & Minerals.

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SURFACE TENSION BY THE RING METHOD - T (c) F (mN) St (mN/m)...

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