Chemistry, asked by Harini280, 10 months ago

The relation ship between viscosity and concentration

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Answered by smitapawar
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Answer:

Answer:The proportionality constant is known as the (dynamic) viscosity ( η, Pa ˣ s ). Increasing the concentration of a dissolved or dispersed substance generally gives rise to increasing viscosity (that is, thickening), as does increasing the relative molecular mass (molecular weight) of a solute.

Answered by lrjinde
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Answer:

Viscosity

Viscosity is a property of fluids that indicates resistance to flow. When a force is applied to a volume of material, then a displacement (deformation) occurs. If two plates (area, A), separated by fluid distance (separation height, H) apart, are moved (at velocity V by a force, F) relative to each other, Newton's law states that the shear stress (the force divided by area parallel to the force, F/A, Pa) is proportional to the shear strain rate (V/H, s-1 ). The proportionality constant is known as the (dynamic) viscosity (η, Pa ˣ s ).

 

Elastic and sliding components of the displacement

caused by shear stress

 

The effect (shear strain) is quantified by the displacement per unit height (D/H) and the rate of this effect (strain rate) is the velocity per unit height (V/H), where the height is the distance to a relatively unaffected position. The viscosity (η) is the tendency of the fluid to resist flow and is defined by:

 

 

Increasing the concentration of a dissolved or dispersed substance generally gives rise to increasing viscosity (that is, thickening), as does increasing the relative molecular mass (molecular weight) of a solute.

 

Comparison of Newtonian, shear-thinning

and shear-thickening fluids

 

 

 

 

 

 

 

 

With Newtonian fluids (typically water and solutions containing only low molecular mass material) the viscosity is independent of shear strain rate and a plot of shear strain rate (for example, the rate of stirring) against shear stress (for example, force, per unit area stirred, required for stirring) is linear and passes through the origin.

 

S-Shaped dependency of log(viscosity) on log(shear rate)

 

 

 

 

At moderate concentrations above a critical value (C*, [244]), hydrocolloid solutions exhibit non-Newtonian behavior where their viscosity depends on the shear strain rate. It is shown typically as opposite, where γ is the shear strain rate, η0 and η∞ are the viscosities at zero and infinite shear strain rate respectively, and τ is a shear-dependent time constant that represents the reciprocal of the shear strain rate required to halve the viscosity.

Explanation:

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