Problem: A 100.0-ml buffer solution is 0.100 M in NH3 and 0.125 M in NH4Br. What mass of HCl can this buffer neutralize before the pH falls below 9.00? If the same volume of the buffer were 0.250 M in NH3 and 0.400 M in NH4Br, what mass of HCl could be handled before the pH fell below 9.00?

FREE Expert Solution

A) 

Calculate the buffer ratio for pH = 9.

Recall the Henderson-Hasselbalch equation:

pH=pKa+logconjugate baseweak acid


pKa of NH4+= 9.24

pH=pKa+log(conjugate baseweak acid)9.0=9.24+log(conjugate baseweak acid)log(conjugate baseweak acid) = 9.0-9.24log(conjugate baseweak acid) = -0.24conjugate baseweak acid =10(-0.24) conjugate baseweak acid =0.575


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Problem Details

A 100.0-ml buffer solution is 0.100 M in NH3 and 0.125 M in NH4Br. What mass of HCl can this buffer neutralize before the pH falls below 9.00? 

If the same volume of the buffer were 0.250 M in NH3 and 0.400 M in NH4Br, what mass of HCl could be handled before the pH fell below 9.00?

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