Which of the following can behave both as a Brønsted–Lowry acid and as a Brønsted–Lowry base? (a) HCO3- (b) CN- (c) H2O (d) H2CO3

Verified step by step guidance

Step 1: Understand the Brønsted–Lowry acid-base theory, which defines an acid as a substance that can donate a proton (H⁺) and a base as a substance that can accept a proton.

Step 2: Analyze each option to determine if it can donate a proton (acting as an acid) and accept a proton (acting as a base).

Step 3: Consider option (a) HCO₃⁻. As an acid, it can donate a proton to form CO₃²⁻. As a base, it can accept a proton to form H₂CO₃.

Step 4: Consider option (b) CN⁻. It can accept a proton to form HCN, but it cannot donate a proton, so it cannot act as an acid.

Step 5: Consider option (c) H₂O. It can donate a proton to form OH⁻ (acting as an acid) and accept a proton to form H₃O⁺ (acting as a base).

Key Concepts

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

Brønsted–Lowry Acid-Base Theory

The Brønsted–Lowry theory defines acids as proton donors and bases as proton acceptors. This framework allows for the classification of substances based on their ability to either donate or accept hydrogen ions (H+). Understanding this theory is essential for identifying compounds that can act as both acids and bases, known as amphoteric substances.

Amphoteric Substances

Amphoteric substances are those that can act as either an acid or a base depending on the reaction conditions. For example, water (H2O) can donate a proton to become hydroxide (OH-) or accept a proton to form hydronium (H3O+). Recognizing amphoteric behavior is crucial for solving questions related to acid-base reactions.

Common Examples of Brønsted–Lowry Acids and Bases

Familiarity with common Brønsted–Lowry acids and bases helps in identifying their behavior in reactions. For instance, bicarbonate (HCO3-) can act as an acid by donating a proton to form carbonate (CO3^2-), or as a base by accepting a proton to form carbonic acid (H2CO3). This knowledge aids in determining which substances in the question can exhibit dual behavior.

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Guided course

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Bronsted-Lowry Acids and Bases Example

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