Question

Calculate the molarity of 0.300 mol of Na2S in 1.75 L of solution.

Answer 1

First equation:
molarity=
no.of moles of solute (Na2S)/volume of solution
0.300/1.75 = 0.171
second equation:
same law
but in volume it is milliliter so you have to convert it by multiplying it with 10^-3
(10 power -3)

to understand it clearly
see this
http://imgur.com/xTS35QM