6.25 g of gaseous HCl are dissolved in water to give a final solution of 25.2 mL .?

Question

What is the pH of the above solution ?

Answer 1

Find the moles of HCl:

n = m/Mm = 6.25/36.5 = 0.17 mol (approx.) where Mm = 36.5 the molar mass of HCl.

Next find the concentration C of the HCl solution:

C = n/V = 0.17/0.0252 = 6.795 mol/L (or 6.975 M)

HCl is a strong acid, it reacts with H2O completely:

HCl + H2O --> Cl- + H3O+

So the concentration of H3O+ ions is 6.975 M

pH = -log[H3O+] = -log6.975 = -0.83