In: Chemistry
Determine the pH of 50.0 mL of a 0.100 M solution of propanoic acid after the following additions. 0.00 mL of 0.100 M NaOH, 30.00 mL of 0.100 M NaOH, 50.00 mL of 0.100 M NaOH, 60.00 mL of 0.100 M NaOH
millimoles of acid = 50 x 0.1 = 5
pKa of acid = 4.89
1) 0.00 mL of 0.100 M NaOH
pH = 1/2 [pKa - logC]
pH = 1/2 [4.89 -log 0.1]
pH = 2.94
2) 30.00 mL of 0.100 M NaOH
millimoles of NaoH = 0.1 x 30 = 3
HA + NaOH ------------------> NaA + H2O
5 3 0 0
2 0 3 3
pH = pKa + log [NaA/ HA]
pH = 4.89 + log (3 / 2)
pH = 5.06
3) 50.00 mL of 0.100 M NaOH
it is equivalence point . here only salt remains both acid and base consumed
salt concetration = 5 / ( 50 + 50) = 0.05 M
pH = 7 + 1/2 [pKa + logC]
pH = 7 + 1/2 [4.89 + log 0.05]
pH = 8.79
4) 60.00 mL of 0.100 M NaOH
[OH-] = (6 - 5) / 110
= 9.09 x 10^-3 M
pOH = -log [OH-]
pOH = -log (9.09 x 10^-3)
pOH = 2.04
pH + pOH = 14
pH = 11.96