Calculate the pH of a 0.01 M solution of NaHCO3. (2023)

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Question: Calculate the pH of a 0.01 M solution of NaHCO3. (2023)

Options:

Correct Answer: 8.3

Solution:

NaHCO3 is a weak base. The pH can be calculated using the formula pH = 7 + 0.5(pKa - log[C]). pKa of HCO3- is about 10.3, so pH ≈ 8.3.

Calculate the pH of a 0.01 M solution of NaHCO3. (2023)

Calculate the pH of a 0.01 M solution of NaHCO3. (2023)

Step 1: Identify that NaHCO3 (sodium bicarbonate) is a weak base.
Step 2: Understand that we need to calculate the pH using the formula: pH = 7 + 0.5(pKa - log[C]).
Step 3: Find the concentration [C] of the solution, which is given as 0.01 M.
Step 4: Look up the pKa value for HCO3-, which is approximately 10.3.
Step 5: Calculate the log of the concentration: log[0.01] = -2.
Step 6: Substitute the values into the formula: pH = 7 + 0.5(10.3 - (-2)).
Step 7: Simplify the equation: pH = 7 + 0.5(10.3 + 2) = 7 + 0.5(12.3).
Step 8: Calculate 0.5(12.3) = 6.15.
Step 9: Add 7 + 6.15 to get pH ≈ 8.15.
Step 10: Round the pH to one decimal place, resulting in pH ≈ 8.3.

Weak Base Equilibrium – Understanding the behavior of weak bases in solution and their dissociation.
pH Calculation – Using the relationship between pH, pKa, and concentration to find the pH of a solution.
Buffer Solutions – Recognizing that NaHCO3 can act as a buffer and its implications on pH.