Acid-Base Quizlet

Buret

A long, glass tube with very accurate markings (accurate to ±0.05 mL) with an open top and a stopcock on the bottom used for titrations.

Phenylphthalein

A pH indicator that is colorless in acid and red-magenta in base.

Litmus

A pH indicator that is pink-red in acid and dark blue in base.

Titration

A quantitative chemical technique whereby the amount of a substance is determined by adding a known volume and concentration of a reactant until the equivalence point is reached.

Standard solution

A solution prepared with great accuracy using volumetric glassware and an analytical balance.

Buffer

A solution usually consisting of an equimolar mixture of a weak acid and its conjugate base that resists changes in pH when small amounts of acid or base are added.

Strong acid

A strong acid completely dissociates into H+ ion(s) and an anion when dissolved in water. This also makes a strong acid a strong electrolyte. There are only 6 strong acids (memorize these): hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid and perchloric acid.

Amphoteric substance

A substance that can act as either an acid or a base. Water can accept or donate a H+ ion (a proton) depending on the chemical reaction.

Weak acid

A weak acid only partially dissociates into H+ ion(s) and an anion when dissolved in water. There are thousands of weak acids.

pH indicator

A weak acid or base that changes color over a narrow pH range. The indicator is one color when protonated, and another color when deprotonated.

Electrolyte

An electrolyte is a substance that forms ions in aqueous solution. ALL ionic compounds that DISSOLVE in water are electrolytes. ALL acids and bases are electrolytes (some are ionic and some are covalent molecules). Strong acids and bases are strong electrolytes and weak acids and bases are weak electrolytes. Remember, electrolytes carry electrical charge.

Carboxylic acid (not required for 2019)

An organic compound that contains a carboxylic acid group, such as acetic acid, HC2H3O2. All organic acids are weak acids. Organic acids are carbon-containing compounds with a carboxylic acid group: -CO2H

Organic compound (not required for 2019)

Any covalent compound that contains carbon atoms.

Arrhenius Acid-Base Theory

Arrhenius defined acids and bases by what ions they dissociate into when dissolved in water. An Arrhenius acid dissociates into H+ ions and an anion when dissolved in water. An Arrhenius base dissociates into OH- ions and a cation when dissolved in water.

Bronsted-Lowry Acid-Base Theory

Bronsted and Lowry defined acids and bases depending on whether they donated or accepted H+ ions (protons). This may happen in aqueous solution or it may not. Water doesn't matter in the definition. A Bronsted-Lowry Acid is a compound that donates a proton (H+ ion). A Bronsted-Lowry Base is a compound that accepts a proton (H+ ion).

Hydronium ion

H3O+. It's a water molecule hat has acquired a proton (H+ ion)

Kw

Kw is the equilibrium constant for water. It has a special name: ion product constant for water. It is a constant and has the value of 1E-14 at 25 ˚C. Kw = [H+][OH-] = (1E-7) x (1E-7) = 1E-14 at 25 ˚C

Weak bases

NH3 (ammonia), insoluble hydroxides (everything that isn't a strong base that contains an OH group is an insoluble hydroxide) and all organic compounds with -NH2 groups are weak bases. Weak bases are weak electrolytes.

Equivalence point

The equivalence point in an acid-base reaction is when [H+] = [OH-]. Usually, this is indicated by a color change marking the endpoint of the reaction. The endpoint is usually chosen to be VERY close to the equivalence point.

Strong bases

The hydroxides of alkali metals and calcium hydroxide, barium hydroxide and strontium hydroxide. Strong bases completely dissociate in water to form hydroxide ions and are strong electrolytes.

Titrant

The standard solution filling the buret.

Analyte

The substance in the flask below the buret that is being reacted with the titrant that fills the buret. The analyte is the substance the amount of which is being determined.

pH

pH = -log[H+] in aqueous solution

pOH

pH = -log[OH-] in aqueous solution

pKw

pKw = -logKw = 14 in aqueous solution