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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 36

An aqueous solution of an unknown solute is tested with litmus paper and found to be acidic. The solution is weakly conducting compared with a solution of NaCl of the same concentration. Which of the following substances could the unknown be: KOH, NH3, HNO3, KClO2, H3PO3, CH3COCH3 (acetone)?

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Acidity and pH

Acidity refers to the concentration of hydrogen ions (H+) in a solution, which determines its pH level. A solution with a pH less than 7 is considered acidic. In this context, the unknown solute must produce H+ ions when dissolved in water, indicating it is an acid.
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Electrical Conductivity of Solutions

The electrical conductivity of a solution is influenced by the presence of ions, which carry electric charge. Strong electrolytes, like NaCl, dissociate completely into ions, leading to high conductivity. Weak electrolytes, such as weak acids or bases, only partially dissociate, resulting in lower conductivity, which is relevant for identifying the unknown solute.
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Classification of Solutes

Solutes can be classified as strong acids, weak acids, strong bases, weak bases, or neutral substances based on their behavior in solution. Strong acids fully dissociate in water, while weak acids do not. Understanding this classification helps in determining which of the given substances could be the unknown solute based on its acidic nature and conductivity.
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