When the concentration is expressed as the number of moles of a solute per litre of solution,it is known as:

Which of the following methods of expressing concentration are unitless?

Calculate the molarity of a solution of ethanol in water in which the mole fraction of ethanol is $0.040$ (assume the density of water to be $1 \, g/mL$).

The molality of a solution,when $18 \ g$ of glucose is added to $18 \ g$ of $H_2O$,is: (in $m$)

Give the meaning of $10\%$ glucose by weight.

$A$ sample of drinking water is found to be severely contaminated with chloroform $(CHCl_3)$,which is a suspected carcinogen. The level of contamination is $15 \ ppm$ (by mass). Calculate the molarity of chloroform in the water sample.