In: Chemistry
What is the pH in a titration of 125 mL of 0.45 F sulfurous acid (H2SO3) with a 1.23 M solution of sodium hydroxide before any base is added?
Volume of H2SO3 = 125 mL = 0.125 L
Molarity of H2SO3 = 0.45 M
Moles of H2SO3 = Molarity x volume
=0.45 M x 0.125 L
=0.05625 mol
Ka of H2SO3 = 1.2 x 10-2
H2SO3 | H2O <===> | H3O+ | HSO3- | |
Initial | 0.05625 mol | - | 0 | 0 |
Change | -x | - | +x | +x |
equilibrium | 0.05625-x | - | x | x |
By solving the above quadratic equation
using formula
We get x = 0.0207
Concentration of H3O+ = 0.0207 M
pH = -log[H3O+]
pH = -log[0.0207]
pH = -(-1.68)
pH = 1.68