Problem: Calculate the pH of a solution that is 0.40 M H2NNH2 and 0.80 M H2NNH3NO3. In order for this buffer to have pH = pKa, would you add HCl or NaOH? What quantity (moles) of which reagent would you add to 1.0 L of the original buffer so that the resulting solution has pH = pKa?

🤓 Based on our data, we think this question is relevant for Professor Radnia's class at Louisiana State University - Shreveport.

FREE Expert Solution

0.40 M H2NNH2 → weak base/conjugate base

0.80 M H2NNH3NO3

H2NNH3NO3 → H2NNH3+ + NO3-

H2NNH3+ → conjugate acid/weak acid


Calculate pKa:

Kb of H2NNH2 = 3.0x10-6

KwKb=Ka·KbKbKa=KwKbKa=1.0×10-143.0×10-6

Ka = 3.33x10-9


pKa=-log KapKa=-log (3.33×10-9)

pKa = 8.48


Calculate pH:

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Problem Details

Calculate the pH of a solution that is 0.40 M H2NNH2 and 0.80 M H2NNH3NO3. In order for this buffer to have pH = pKa, would you add HCl or NaOH? What quantity (moles) of which reagent would you add to 1.0 L of the original buffer so that the resulting solution has pH = pKa?

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Buffer concept. You can view video lessons to learn Buffer. Or if you need more Buffer practice, you can also practice Buffer practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Radnia's class at Louisiana State University - Shreveport.

What textbook is this problem found in?

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.