Answer : When we consider the atmospheric pressure as 1 atm then according to the ideal gas equation we can find out the molar mass of any unknown by this formula ;
PV=nRT
so if the pressure increases than 1 atm then we can see from the above equation that it will result in greater value for the number of moles (n) in the above equation.
While n = m/M where m is mass of the unknown in g and M is molecular mass.
So, if pressure is higher then it will result in molar mass of unknown which is much smaller.
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
