In: Chemistry
A chemist synthesized a monoprotic weak acid, (HA) and 2.00 mmol of the solid acid is dissolved in 100.0 ml of water. The acid is titrated with 20.0 ml of 0.0500 M NaOH. If the final solution has a pH of 6.00, what's the Ka of the acid?
PH = 6.00
weak acid = 2.0 m mol= 2.0x10^-3 = 0.002 mole
NaOH = 20.0ml 0f 0.0500M
Number of moles of NaOH = 0.05x0.02 L =0.001 mole
HA + NaOH --------------- NaA + H2O
0.002 mol 0.001 mole 0 0
0.002-.0001 0.001-0.001 0.001
0.001 0 0.001
Number of moles of HA = 0.001 mole
Number of moles of NaA = 0.001 moles
PH= PKa + log[salt/acid]
6.00 = PKa + log[0.001/0.001]
6.00 = PKa + 0
PKa = 6.0
-log[ka] = 6.0
Ka = 10^-6.0
Ka = 10^-6