a buffer solution with pH=9 is to be prepared by mixing Nh4cl and Nh4Oh calculate no. of moles Nh4cl that should be added to 1Litre of 1.0M Nh4OH Kb=1.8*10^-5
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● Answer -
1.8 moles
● Explanation -
pOH of desired buffer is calculated by -
pOH = 14 - pH
pOH = 14 - 9
pOH = 5
By Hendersan-Hasselbach eqn,
pOH = pKb + log([salt]/[base])
pOH = -log(Kb) + log([NH4Cl]/[NH4OH])
Substituting values,
5 = -log(1.8×10^-5) + log([NH4Cl]/1)
5 - 4.745 = log[NH4Cl]
0.255 = log[NH4Cl]
Taking antilog,
[NH4Cl] = 1.8 M
To prepare 1.8 M NH4Cl soln, 1.8 moles of NH4Cl are to be added in 1 L soln.
Hope this helps you...
1.8 moles
● Explanation -
pOH of desired buffer is calculated by -
pOH = 14 - pH
pOH = 14 - 9
pOH = 5
By Hendersan-Hasselbach eqn,
pOH = pKb + log([salt]/[base])
pOH = -log(Kb) + log([NH4Cl]/[NH4OH])
Substituting values,
5 = -log(1.8×10^-5) + log([NH4Cl]/1)
5 - 4.745 = log[NH4Cl]
0.255 = log[NH4Cl]
Taking antilog,
[NH4Cl] = 1.8 M
To prepare 1.8 M NH4Cl soln, 1.8 moles of NH4Cl are to be added in 1 L soln.
Hope this helps you...
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