Hydrogen Ions and pH

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Self-Ionization Noun

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[self-ahy-uh-ni-zey-shuhn]

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Self-Ionization

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The process where a substance, like water, reacts with itself to form ions, such as hydronium and hydroxide.

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Example: This diagram shows two water molecules reacting to form a hydronium ion (H₃O⁺) and a hydroxide ion (OH⁻), illustrating the process of self-ionization.

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Hydronium Ion Noun

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[hahy-droh-nee-uhm ahy-on]

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Hydronium Ion

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The positively charged ion H₃O⁺, created when a water molecule accepts a proton, representing the hydrogen ion in aqueous solutions.

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Example: This image shows the molecular structure of a hydronium ion, which consists of one oxygen atom and three hydrogen atoms, and is found in water.

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Hydroxide Ion Noun

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[hahy-drok-sahyd ahy-on]

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Hydroxide Ion

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The negatively charged polyatomic ion OH⁻, whose concentration determines the basicity or alkalinity of an aqueous solution.

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Example: This diagram shows a hydroxide ion, which is made of one oxygen atom and one hydrogen atom bonded together and carrying a negative charge.

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Hydrogen Ion Noun

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[hahy-druh-juhn ahy-on]

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Hydrogen Ion

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A single proton, represented as H⁺, which has lost its electron; its concentration is a measure of a solution's acidity.

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Example: A hydrogen ion (a proton) joins with a water molecule to form a positively charged hydronium ion, which determines the acidity (pH) of a solution.

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Ion Product Constant for Water (Kw) Noun

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[ahy-on prod-uhkt kon-stuhnt for waw-ter]

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Ion Product Constant for Water (Kw)

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The equilibrium constant for water's self-ionization, representing the product of the hydrogen and hydroxide ion concentrations in an aqueous solution.

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Example: This image shows how two water molecules can trade a hydrogen ion, creating a hydronium ion (H₃O⁺) and a hydroxide ion (OH⁻) in a reversible reaction.

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Le Châtelier's Principle Noun

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[luh shah-tuh-lyeyz prin-suh-puhl]

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Le Châtelier's Principle

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A chemical principle stating that a system at equilibrium will shift its position to counteract any applied change or stress.

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Example: When a stress (like adding more water to one side) is applied to a system at equilibrium, the system shifts to counteract the stress and establish a new equilibrium.

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Acidic Solution Noun

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[uh-sid-ik suh-loo-shuhn]

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Acidic Solution

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An aqueous solution containing a higher concentration of hydrogen ions (H⁺) than hydroxide ions (OH⁻), resulting in a pH below 7.

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Example: This pH scale shows that acidic solutions have a pH value less than 7, with lower numbers indicating stronger acidity.

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Basic Solution Noun

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[bey-sik suh-loo-shuhn]

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Basic Solution

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An aqueous solution containing a lower concentration of hydrogen ions (H⁺) than hydroxide ions (OH⁻), resulting in a pH above 7.

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Example: When a base like sodium hydroxide (NaOH) is added to water, it splits into ions, releasing hydroxide ions (OH⁻), which makes the solution basic.

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Neutral Solution Noun

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[noo-truhl suh-loo-shuhn]

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Neutral Solution

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An aqueous solution where the concentrations of hydrogen ions and hydroxide ions are equal, resulting in a pH of exactly 7.0.

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Example: This image shows that when pH paper is dipped into a neutral solution, it turns green, indicating a pH level that is neither acidic nor basic.

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pH Noun

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[pee-eych]

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pH

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A logarithmic scale used to specify the acidity or basicity of an aqueous solution, calculated as the negative logarithm of [H⁺].

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Example: The pH scale measures how acidic or basic a substance is, with everyday examples like lemons being acidic and ammonia being basic.