Ammonia, NH3, acts as an Arrhenius base, a Brønsted-Lowry base, and a Lewis base, in aqueous solution. Write out the reaction NH3 undergoes with water and explain what properties of ammonia correspond to each of the three definitions of “base.”

Verified step by step guidance

Step 1: Write the chemical equation for the reaction of ammonia (NH3) with water (H2O). Ammonia accepts a proton (H+) from water, forming ammonium ion (NH4+) and hydroxide ion (OH-). The equation is: NH3 + H2O ⇌ NH4+ + OH-.

Step 2: Explain the Arrhenius base definition. An Arrhenius base is a substance that increases the concentration of hydroxide ions (OH-) in aqueous solution. In this reaction, NH3 increases the OH- concentration, thus acting as an Arrhenius base.

Step 3: Explain the Brønsted-Lowry base definition. A Brønsted-Lowry base is a substance that can accept a proton (H+). In this reaction, NH3 accepts a proton from H2O to form NH4+, demonstrating its role as a Brønsted-Lowry base.

Step 4: Explain the Lewis base definition. A Lewis base is a substance that can donate an electron pair. NH3 has a lone pair of electrons on the nitrogen atom, which it can donate to form a bond with a proton (H+), thus acting as a Lewis base.

Step 5: Summarize the properties of NH3 in the context of these definitions. NH3 acts as an Arrhenius base by increasing OH- concentration, as a Brønsted-Lowry base by accepting a proton, and as a Lewis base by donating an electron pair.

Key Concepts

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

Arrhenius Base

An Arrhenius base is defined as a substance that increases the concentration of hydroxide ions (OH-) in aqueous solution. In the case of ammonia (NH3), it reacts with water to produce ammonium ions (NH4+) and hydroxide ions (OH-), thus raising the pH of the solution. This behavior exemplifies the Arrhenius definition, as NH3 contributes to the formation of OH- ions.

Brønsted-Lowry Base

According to the Brønsted-Lowry theory, a base is a proton (H+) acceptor. Ammonia acts as a Brønsted-Lowry base when it accepts a proton from water, forming NH4+ and OH-. This interaction highlights ammonia's ability to accept protons, which is a key characteristic of Brønsted-Lowry bases.

Lewis Base

A Lewis base is defined as an electron pair donor. Ammonia can be classified as a Lewis base because it has a lone pair of electrons on the nitrogen atom, which it can donate to form a coordinate covalent bond. In the reaction with water, this electron donation facilitates the formation of NH4+, demonstrating ammonia's role as a Lewis base.

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Lewis Acids and Bases

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