Acid Ka
H2PO4- 6.29 x 10-8
NH4+ 5.68 x 10 -10
HCl >> 1
Calculate the pH of a 0.150 M solution of Na2HPO4.
Calculate the pH of a 0.150 M solution of NH4NO3.
Calculate the pH of a 0.150 M solution of KCl.
1) Na2HPO4 is salt of weak acid H2PO4- and strong base NaOH
for such salts
pH = 1/2 [pKw + pKa + logC]
pKa = - log Ka = - log [6.29 x 10-8] = 7.20
pH = 1/2 [14 + 7.20 + log 0.150]
pH = 10.19
2) NH4NO3 is salt of weak base and strong acid
pKa of NH4+ = - log [5.68 x 10-10] = 9.24
pKb = 14 - 9.24 = 4.76
pOH = 1/2 [pKw + pKb + log C]
pOH = 1/2 [14 + 4.76 + log 0.150]
pOH = 8.97
pH = 14 - 8.97
pH = 5.03
3) KCl is salt of strong acid and strong base
such salts pH always 7.0
pH = 7.0
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