Question

Calculate the ph of a solution that is 0.100 m hno2 and 1.00 m nano2

Answer 1

The pH of a solution that is 0.100 M HNO2 and 1.00 M NaNO2 is calculated using the Henderson-Hasselbalch equation, which involves the pKa of nitrous acid and the ratio of the conjugate base to acid concentration. Assuming a pKa of 3.25 for HNO2, the pH is determined to be 4.25.

Step-by-step explanation:

To calculate the pH of a solution that is 0.100 M HNO2 and 1.00 M NaNO2, we must recognize that this is a buffer system consisting of a weak acid (HNO2) and its conjugate base (NO2- from NaNO2).

For such a buffer system, we can use the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])

Where pKa is the acid dissociation constant for HNO2, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid.

We need to find the pKa for HNO2. The dissociation reaction for HNO2 is:

HNO2 (aq) ← H+ (aq) + NO2- (aq)

Let's assume the pKa for nitrous acid (HNO2) is around 3.25 (the exact value can vary slightly, but this is a commonly cited rough estimate).

Now, using the Henderson-Hasselbalch equation:

• 
  
• pH = 3.25 + log(1.00 / 0.100)
• 
  
• pH = 3.25 + log(10)
• 
  
• pH = 3.25 + 1
• 
  
• pH = 4.25

Therefore, the pH of the solution is 4.25.

Answer 2

HNO₂ and NaNO₂ is considered as acidic buffer because HNO₂ is considered as weak acid and NaNO₂ is the conjugate base of this acid.

To find the original pH, we just use the Henderson-Hasselbach equation:
pH = pKa + log
`([Salt])/([Acid])`

so pH = 3.4 + log
`((1.0 M))/((0.1 M))` = 4.4