Which one of the following is a weak acid

General
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which one of the following is a weak acid

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Which one of the following is a weak acid?

Answer:

To determine which acid among a given list is a weak acid, it is important first to understand the definitions and characteristics of strong and weak acids.

Strong Acids:

Strong acids dissociate completely (or nearly completely) in water, releasing a high concentration of {H^+} ions. Common examples of strong acids include:

  1. Hydrochloric acid (HCl)
  2. Sulfuric acid (H₂SO₄)
  3. Nitric acid (HNO₃)

Weak Acids:

Weak acids only partially dissociate in water, releasing a relatively lower concentration of {H^+} ions. Common examples of weak acids include:

  1. Acetic acid (CH₃COOH)
  2. Citric acid (C₆H₈O₇)
  3. Hydrofluoric acid (HF)

Since specifics of the given list are not provided in the initial question, here we’ll discuss some common scenarios that students typically encounter:

Common Examples for Identification:

  1. Hydrochloric Acid (HCl) - This is a strong acid.
  2. Acetic Acid (CH₃COOH) - This is a weak acid.
  3. Nitric Acid (HNO₃) - This is a strong acid.
  4. Sulfuric Acid (H₂SO₄) - This is a strong acid.
  5. Hydrocyanic Acid (HCN) - This is a weak acid.

Given a typical list like the one above, Acetic Acid (CH₃COOH) stands out as a classic example of a weak acid.

Detailed Analysis:

1. Acetic Acid (CH₃COOH):

  • Dissociation in Water:

    CH_3COOH \leftrightarrow CH_3COO^- + H^+

    This equilibrium lies significantly to the left, indicating only partial dissociation.

  • Acid Dissociation Constant (Ka):
    Acetic acid has a relatively low {Ka} value (approximately 1.8 \times 10^{-5}), reinforcing its classification as a weak acid.

General Properties of Weak Acids:

  • Partial Ionization: Unlike strong acids, weak acids only partly ionize in solution.
  • pH Value: Weak acids typically have higher {pH} values compared to strong acids of the same concentration.
  • Conductivity: Solutions of weak acids conduct electricity poorly due to fewer ions in solution.
  • Reaction with Metals: Weak acids react slower with metals compared to strong acids.

Identifying Weak Acids:

In summary, when you need to identify a weak acid in a list, look for those known for partial dissociation and lower {Ka} values. Without knowing the exact list, we could conclude, based on the examples provided, that Acetic Acid (CH₃COOH) is a common weak acid among typical choices.

Hope this comprehensive breakdown on weak acids clarifies the concept for you! If you have a specific list to evaluate further, feel free to share it for more tailored assistance.