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Acid
A substance that has the potential to donate a proton or accept an electron pair.
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Acidic
Having a pH less than 7.
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Base
A substance that can accept a proton, release OH-, or donate an electron pair.
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Basic
A solution with a pH greater than 7.
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Buffer
A solution composed of an acid and its conjugate base that serves to moderate the pH of the solution.
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Conjugate Acid
A molecule that can be described as a base that has gained one proton.
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Conjugate Base
A molecule that can be described as an acid that has lost one proton.
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Endpoint
The volume or amount of acid or base added to a solution to neutralize the unknown solution during a titration. When using an indicator, the endpoint occurs when enough titrant has been added to change the color of the indicator.
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Equivalence Point
The volume of titrant and pH at which the amount of acid equals the amount of base present in the original solution, or the amount of base equals the amount of acid present in the original solution.
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Indicator
A molecule whose conjugate acid or conjugate base has a different color. An indicator is used to mark a certain pH level.
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pH
A measure of the hydrogen ion concentration, it is equal to - log [H+].
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pKa
A measure of the strength of an acid, it is equal to - log Ka, where Ka is the acid dissociation constant in water.
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pKb
A measure of the strength of a base, it is equal to - log Kb, where Kb is the base dissociation constant in water.
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Strong Acid
An acid with a pKa less than zero. Strong acids completely dissociate in water.
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Strong Base
A base with a pKb less than zero. Strong bases completely dissociate in water.
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Titrant
The acid or base of known amount and concentration that is added to the unknown solution during an acid-base titration.
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Titration
An experiment where an unknown concentration of acid or base is neutralized with a known volume and concentration of acid or base to determine the concentration of the unknown.
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Titration Curve
A plot of solution pH versus titrant volume during a titration.
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Weak Acid
An acid with a pKa greater than zero. Weak acids do not completely dissociate in water.
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Weak Base
A base with a pKb greater than zero. Weak bases do not completely dissociate in water.