Problem: An aqueous solution contains dissolved C6H5NH3Cl and C6H5NH2. The concentration of C6H5NH2 is 0.50 M and pH is 4.20.a. Calculate the concentration of C6H5NH3+ in this buffer solution.

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FREE Expert Solution

For this, we shall use the Henderson-Hasselbalch equation as in:

pOH = pKb + logconjugate acidweak base

  • C6H5NH2 is a weak base → According to Bronsted-Lowry definition, a base is a proton (H+) acceptor.
  • C6H5NH3is the conjugate acid conjugate acid of a base is simply the compound formed when a base gains a hydronium ion (H+). It's considered as an acid because it can lose H+ to reform the base.


We can get pOH from pH and pKb from Kb.

pOH = 14-pHpOH = 14-4.20

pOH = 9.80


pKb =-log KbpKb =-log 3.8×10-10

pKb = 9.42


Substituting in the equation:

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Problem Details

An aqueous solution contains dissolved C6H5NH3Cl and C6H5NH2. The concentration of C6H5NH2 is 0.50 M and pH is 4.20.

a. Calculate the concentration of C6H5NH3+ in this buffer solution.

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Based on our data, we think this problem is relevant for Professor Fatima's class at UWATERLOO.

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Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl 2nd Edition practice problems.