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Which 0.1 M solution of the following acids has the highest pH? A - VCE - SSCE Chemistry - Question 20 - 2011 - Paper 1
Question 20
Which 0.1 M solution of the following acids has the highest pH? A. nitrous acid B. ethanoic acid C. methanoic acid D. hypobromous acid
Worked Solution & Example Answer:Which 0.1 M solution of the following acids has the highest pH? A - VCE - SSCE Chemistry - Question 20 - 2011 - Paper 1
Step 1
Evaluate the options based on acid strength
Answer
To determine which acid has the highest pH in a 0.1 M solution, we need to consider the strength of each acid. The pH of a solution is inversely related to the concentration of hydrogen ions it produces in solution. The stronger the acid, the lower the pH. Therefore, we will evaluate nitrous acid (HNO₂), ethanoic acid (CH₃COOH), methanoic acid (HCOOH), and hypobromous acid (HBrO) in terms of their dissociation in water and their dissociation constants (Ka).
Step 2
Consider the dissociation constants (Ka)
Answer
- Nitrous Acid (HNO₂) has a Ka of approximately 4.5 × 10⁻₴.
- Ethanoic Acid (CH₃COOH) has a Ka of approximately 1.8 × 10⁻⁵.
- Methanoic Acid (HCOOH) has a Ka of approximately 1.8 × 10⁻⁴.
- Hypobromous Acid (HBrO) has a Ka of approximately 2.3 × 10⁻⁹.
From these values, it is clear that nitrous acid is the strongest among the listed options, while hypobromous acid is the weakest.
Step 3