Acids and Alkalis

Cards · 20

Acid

A proton (H+) donor with a pH below 7; typically tastes sour, turns blue litmus paper red, and corrodes reactive metals.

Base

A substance that neutralizes acids by accepting protons; has a pH above 7, tastes bitter, and feels slippery.

Alkali

A water-soluble base that releases hydroxide ions (OH-); features a pH above 7 and feels notably soapy to the touch.

Hydrochloric Acid (HCl)

A strong monoprotic acid with a pH around 1 to 2; an aqueous solution that is colorless, pungent, and highly corrosive.

Sulfuric Acid (H2SO4)

A strong diprotic acid with a pH around 0.5 to 1; an oily, colorless liquid with strong dehydrating properties.

Nitric Acid (HNO3)

A strong oxidizing acid with a pH around 1; a fuming, colorless liquid that can turn yellowish over time.

Ethanoic Acid (Acetic Acid)

A weak organic carboxylic acid with a pH of about 2.5 to 3; a clear liquid with a distinct, pungent vinegar odor.

Citric Acid

A weak tricarboxylic acid found in citrus fruits with a pH around 2 to 3; exists as a sour, white crystalline solid.

Carbonic Acid (H2CO3)

A weak, unstable diprotic acid formed by dissolving carbon dioxide in water; maintains a pH around 4 to 5 in fizzy drinks.

Sodium Hydroxide (NaOH)

A strong alkali known as caustic soda with a pH near 14; exists as white, deliquescent solid pellets that dissolve exothermically.

Potassium Hydroxide (KOH)

A strong, highly soluble alkali with a pH around 13 to 14; a caustic, white solid used extensively in alkaline batteries.

Calcium Hydroxide (Ca(OH)2)

A sparingly soluble alkali known as slaked lime; its saturated solution (limewater) has a pH around 12.4 and turns cloudy with CO2.

Ammonia Solution (NH3(aq))

A weak alkali producing ammonium and hydroxide ions, with a pH around 11 to 12; clear with a sharp, suffocating smell.

Magnesium Hydroxide (Mg(OH)2)

A very weak, poorly soluble base used as an antacid; yields a mild pH around 9.5 to 10.5 in suspension (Milk of Magnesia).

Litmus Indicator

A pH indicator extracted from lichens that turns red below pH 4.5 and blue above pH 8.3; used in solution or paper form.

Phenolphthalein

A synthetic indicator that remains colorless in acidic solutions (pH < 8.2) and turns vivid pink in alkaline solutions (pH > 10).

Methyl Orange

An azo dye pH indicator that turns distinctly red in strong acids (pH < 3.1) and bright yellow in neutral/alkaline media (pH > 4.4).

Neutral Substance (Pure Water)

A substance with equal concentrations of H+ and OH- ions; has a neutral pH of 7 at 25 degrees Celsius and is odorless and tasteless.

Universal Indicator

A chemical mixture showing a continuous spectrum of colors from red (strong acid, pH 1-3) to green (pH 7) to purple (strong alkali, pH 14).

Neutralization Reaction

The exothermic chemical reaction where an acid reacts with a base to produce water and a salt, driving the pH toward 7.