A buffer solution is prepared by mixing 50.0 mL of 0.300 M NH3 with 50.0 mL of 0
ID: 633335 • Letter: A
Question
A buffer solution is prepared by mixing 50.0 mL of 0.300 M NH3 with 50.0 mL of 0.300 M NH4Cl. the pKb is 4.74.
Calculate the [NH3] and [H4Cl] in the buffer solution. Calculate the pH of the buffer solution.
7.50 mL of 0.125 M HCl is added to the 100.0 mL of the buffer solution. Calculate the new [NH3] and [NH4Cl] for the buffer solution. Calculate the new pH of the solution.
7.50 mL of 0.125 M NaOH is added to the 100.0 mL of the buffer solution. Calculate the new [NH3] and [NH4Cl] for the buffer solution. Calculate the new pH of the solution.
Explanation / Answer
a)
pOH=pKb+log[salt]/[base]
[NH3]=50*0.3=15
[NH4Cl]=50*0.3=15
pH=14-pOh=14-4.74=9.26
b)
[HCl]=7.5*0.125=0.9
[NH3]=14.1
[NH4Cl]=15.9
pH=14-4.74-log(15.9/14.1)=9.23
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