You prepare a 2nd solution (solution B) by pipetting 10.00 ml of your 1st solution (solution A) into a 50.00 ml volumetric flask and diluting with deionized water to the 50.00 ml mark.
If the concentration of solution B is 0.1045 M NaCl, what was the NaCl concentration of solution A?

Concentration solution A was 0.5225 M

Explanation:

10.00 mL of solution A was diluted to 50.00 mL and yields 50.00 mL of solution B

According to laws of dilution-      

where, and are concentration of solution A and B respectively

and are volumes of solution A and B respectively

Here = 0.1045 M, = 50.00 mL and = 10.00 mL

Hence,

So, concentration solution A was 0.5225 M

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.