Viscosities of Liquids

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The objective of this lab was to find and examine the viscosities of ideal and non-ideal solutions. The ideal being the toluene/p-xylene and the non-ideal being the methanol/water. The second objective of this lab was to investigate the temperature dependence of viscosity (Halpern, 17-1).

Viscosity is the resistance to flow of a certain fluid. In this experiment two solutions are used. According to the definition of viscosity mobile liquids have a relatively low viscosity. Fluidity is the reciprocal of viscosity, given as equation 1: F=1/ η. Fluidity is advantageous because solutions of mixed solutions of nonassociating liquids are roughly additive. In this experiment binary solutions are used, so if each pure liquid has fluidities Fa and Fb, the fluidity of a mixture is given by: Equation1 (Halpern, 17-3). F=xAFA•+xBFB• where Xa and Xb are the mole fractions.

The viscosity of the mixture is given as:
ln η = XA ln η •A + XB ln η •B Equation 2 (Halpern, 17-3)
The second part of this lab is to measure the temperature dependence of viscosity. It is known that the viscosity of a pure liquid will increase exponentially. If the flow time of a liquid is measures and the density is known the viscosity will then be given as: Equation 3 (Halpern 17-5).

η = η r ρt/ ρrtr where μr, ρr,tr are the viscosity, density, and flow time of the reference liquid, in this case water (Halpern, 17-4).

Materials and Methods:
The method for this lab was taken from Halpern pgs 17-4 to 17-6. Materials:
The materials used for this lab were:
Ostwald Viscometer
Digital Thermometer
Hot water bath
5mL pipette

Water was used as a reference liquid. Then a binary solution was made of a 20% methanol in water, 40% methanol in water, 60% methanol in water, 80% methanol in water...
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