pKb = 4.75 and 0.025 molL with respect to NH4Cl.
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Use the Henderson - Hasselbalch equation:
pOH = pKb + log ( [salt]/[base])
pOH = 4.75 + log (0.025/0.027)
pOH = 4.75 + log 0.926
pOH = 4.75 + (-0.03)
pOH = 4.72
pH = 14.00 - 4.72
pH = 9.28
pOH = pKb + log ( [salt]/[base])
pOH = 4.75 + log (0.025/0.027)
pOH = 4.75 + log 0.926
pOH = 4.75 + (-0.03)
pOH = 4.72
pH = 14.00 - 4.72
pH = 9.28