Acids, Bases and Salts - Vocabulary Flashcards (Video Notes)

Vocabulary flashcards covering key terms and definitions from the acids, bases, and salts notes.

Acid

A substance that donates H+ (as H3O+ in water); acids have a sour taste, turn blue litmus red, and produce hydronium ions in solution.

Base

A substance that produces OH− in water; bases have a bitter taste, turn red litmus blue, and form hydroxide ions in solution; alkalis are soluble bases.

Litmus

A natural pH indicator dye; blue litmus turns red in acids, red litmus turns blue in bases; purple indicates neutrality.

Indicator

A substance that changes colour to show whether a solution is acidic or basic (e.g., methyl orange, phenolphthalein, beetroot extract).

pH

A scale (0-14) indicating how acidic or basic a solution is; 7 is neutral,

Hydronium ion (H3O+)

The hydrated proton formed when acids dissolve in water; represents the acidic species in aqueous solutions.

Hydrogen ion (H+)

Proton; in water, it exists mainly as H3O+; responsible for acidity in solutions.

Hydroxide ion (OH−)

An ion responsible for basicity; produced by bases in water.

Neutralisation reaction

A reaction between an acid and a base to form a salt and water (e.g., NaOH + HCl → NaCl + H2O).

Salt

A compound formed from the reaction of an acid and a base; consists of positive and negative ions (e.g., NaCl, CaCO3).

Alkalis

Soluble bases that dissolve in water and produce OH− ions.

Strong acid

An acid that dissociates completely in water, yielding a large concentration of H+.

Weak acid

An acid that only partially dissociates in water, yielding fewer H+ ions.

Strong base

A base that fully dissociates in water, producing a high concentration of OH−.

Weak base

A base that only partially dissociates in water.

Universal indicator

A mixture of indicators used to estimate pH by showing a range of colours at different H+ concentrations.

Water of crystallisation

Water molecules chemically bound within a crystalline salt; e.g., CuSO4·5H2O, CaSO4·2H2O.

Plaster of Paris

Calcium sulfate hemihydrate (CaSO4·0.5H2O) formed by heating gypsum; used with water to form solid plaster.

Bleaching powder

Calcium oxychloride (Ca(ClO)2); produced by reacting chlorine with dry slaked lime; used for bleaching and disinfection.

Chlor-alkali process

Electrolysis of brine (NaCl) to produce chlorine gas, sodium hydroxide (NaOH), and hydrogen gas (H2).

Sodium hydroxide

A strong base produced via the chlor-alkali process; highly soluble in water and widely used in industry.

Baking soda

Sodium hydrogencarbonate (NaHCO3); a mild base used in cooking, baking powder, and as an antacid; decomposes on heating to CO2, H2O, and Na2CO3.

Washing soda

Sodium carbonate (Na2CO3); produced from baking soda by heating; used in cleaning, glass and soap industries.

Carbon dioxide test with lime water

CO2 passed through lime water turns it milky due to formation of calcium carbonate (CaCO3).

Metal oxide + acid

Reaction form a salt and water (e.g., CuO + 2HCl → CuCl2 + H2O).

Metal + acid (hydrogen displacement)

Acid reacts with metal to release hydrogen gas and form a salt.

Metal carbonate + acid

Reaction yields a salt, CO2, and H2O (e.g., Na2CO3 + 2HCl → 2NaCl + CO2 + H2O).

Non-metallic oxide + base

Acidic oxide reacts with base to form a salt and water (e.g., CO2 + Ca(OH)2 → CaCO3 + H2O).

pH paper

Paper impregnated with pH indicators used to estimate the pH of a solution.

Acid rain

Rain with low pH (<5.6) due to acidic pollutants; lowers the pH of rivers and harms aquatic life.

Olfactory indicator

Indicators that change odour in acidic or basic media (e.g., vanilla, onion, clove).

Antacid

A base (often magnesium hydroxide) used to neutralise excess stomach acid.

Tooth enamel and pH

Enamel dissolves if mouth pH drops below about 5.5, leading to tooth decay; cleaning with basic toothpaste helps neutralise acids.