If 500 mL of HCl gas at 300 K and 100 kPa dissolve in 100 mL of pure water, what is the concentration?

1 Answer
Sep 26, 2014

The concentration of HCl is 0.200 mol/L.

You use the Ideal Gas Law to find the number of moles, and then you calculate the molarity.

PV=nRT

n=PVRT=100 kPa × 0.500 L8.314 kPa⋅L⋅K1mol1×300 K = 0.020 05 mol (3 significant figures + 1 guard digit)

If there is no volume change when the HCl dissolves in the water, the volume of the solution is 100 mL.

Molarity = moleslitres=0.02005 mol0.100 L = 0.200 mol/L