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Which of following are dimentioless quantities?1.vapour density2.molality3.specific gravity4.mass fraction also mention method to determne it.

Pranav Dabhade , 8 Years ago
Grade 12th pass
anser 1 Answers
Piyush Kumar Behera

Last Activity: 8 Years ago

See to know whether a quantity is dimensionless or not we have to check through its expression or we have to check that if it is the ratio of some quantities of same dimension. Quantities which are relative measures (taking a reference measure)are also dimensionless.For example:reative density etc.
In this question i will go with the defination 
Vapour Density is the density of a particular gas or vapour relative to that of hydrogen at the same pressure and temperature.So as it is relative,hence dimesionless.
Molality is defined as no. of moles of solute per kg of solvent,hence its unit will be
mol kg-1.Hence it is not dimensionless.
Similarly specific gravity or relative density is a relative measure ,hence it is dimensionless.
As mass fraction is given by the ratio of mass of one substance to the mass of the whole mixture.As the unit will be kg/kg.Hence it is dimension less.
 

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