Question

The question text is cut off in the image, so the full data for this question is not visible. Only the ending part
“\(\dots\) mole of \(CH_3COONa\). The \([H^+]\) in the resultant solution is”
and the given value
\[ K_a(CH_3COOH)=1.1\times 10^{-5} \] are visible. Therefore, the complete numerical information needed to solve this question is missing.

• A. \(1.47\times 10^{-5}\,M\)
• B. \(2\times 10^{-5}\,M\)
• C. \(2.5\times 10^{-5}\,M\)
• D. \(1.5\times 10^{-5}\,M\)
• E. \(0.9\times 10^{-5}\,M\)

Hint:

For acidic buffer solutions, always use \([H^+]=K_a\cdot \frac{[\text{acid}]}{[\text{salt}]}\). But this requires the full acid-to-salt ratio, so incomplete question data cannot give a reliable numerical answer.

Answer 1

Answer: (E)

Step 1: Identify what is visible in the image.
From the image, we can read only the last part of the question: \[ \text{``\(\dots\) mole of } CH_3COONa. \text{ The } [H^+] \text{ in the resultant solution is''} \] along with: \[ K_a(CH_3COOH)=1.1\times 10^{-5} \] and the answer key marked as option \((5)\).

Step 2: Recognize the likely chapter and concept.
Since both \(CH_3COOH\) and \(CH_3COONa\) are involved, this is clearly a buffer solution question involving acetic acid and sodium acetate. In such questions, the hydrogen ion concentration is usually found using: \[ [H^+]=K_a\cdot \frac{[\text{acid}]}{[\text{salt}]} \]

Step 3: State what is missing.
To apply the buffer formula correctly, we need the full quantities of: \[ \text{moles of } CH_3COOH \quad \text{and} \quad \text{moles of } CH_3COONa \] or equivalent concentration-volume data. That part is cut off in the image.

Step 4: Explain why the question cannot be solved uniquely from the visible image alone.
Without the complete first line of the question, the ratio \[ \frac{[\text{acid}]}{[\text{salt}]} \] cannot be determined. Since \([H^+]\) depends directly on this ratio, the numerical answer cannot be derived reliably from the visible portion only.

Step 5: Avoid unsupported reconstruction.
Although the official answer shown is option \((5)\), it would not be mathematically reliable to reconstruct the missing data by guesswork. Therefore, the exact derivation cannot be written from this image alone.

Step 6: What would be done if full data were visible.
If the complete question were visible, we would use: \[ [H^+]=K_a\cdot \frac{\text{moles of acid}}{\text{moles of salt}} \] and then substitute: \[ K_a=1.1\times 10^{-5} \] to compute the final value.

Step 7: Final statement.
So, based on the image alone, the full solution cannot be reconstructed exactly, but the answer key shown in the image marks: \[ \boxed{0.9\times 10^{-5}\,M} \] as the correct answer.