Chemistry Properties, Reactions, and Gas Tests for Acids and Bases

Properties of acids

Sour, corrosive, pH < 7, react with bases to form salts + water, turn blue litmus red

Properties of bases

Bitter, slippery, pH > 7, react with acids to form salts + water, turn red litmus blue

Difference between base and alkali

Base neutralises acids; alkali is a base that dissolves in water

How is pH scale determined?

By the concentration of hydrogen ions [H⁺]

What are pH indicators?

Chemicals that change colour in acids or bases

What does pH < 7 mean?

Acidic solution

What does pH > 7 mean?

Basic/alkaline solution

Acid + active metal → ?

Metal salt + hydrogen gas

Acid + metal hydroxide → ?

Metal salt + water

Acid + metal oxide → ?

Metal salt + water

Acid + metal carbonate → ?

Metal salt + carbon dioxide + water

Acid + metal hydrogen carbonate → ?

Metal salt + carbon dioxide + water

Combination reaction general equation

Substance A + Substance B → Substance C

Hydrogen combustion equation

Hydrogen + oxygen → water + energy

Carbon combustion equation

Carbon + oxygen → carbon dioxide + energy

Hydrocarbon combustion equation

Hydrocarbon + oxygen → carbon dioxide + water + energy

Decomposition reaction equation

Substance C → Substance A + Substance B

Acids + metals → ?

Salt + hydrogen gas

Acids + bases → ?

Salt + water (neutralisation)

Acids + carbonates → ?

Salt + carbon dioxide + water

What is neutralisation?

Reaction between acid and base to form salt + water

How to make a solution neutral?

Add the right amount of acid to a base (or vice versa)

Define combustion reaction

Reaction with oxygen that releases energy (heat/light)

What happens in combustion?

Fuel burns in oxygen, releasing energy + producing oxides

Reactants and products of combustion?

Reactants = fuel + oxygen; Products = oxides + energy

Test for hydrogen gas

Lit splint "pops"

Test for oxygen gas

Glowing splint relights

Test for carbon dioxide gas

Turns limewater cloudy

What is an exothermic reaction?

Reaction that releases energy

What is an endothermic reaction?

Reaction that absorbs energy

How to classify exothermic vs endothermic

Exothermic = releases heat; Endothermic = absorbs heat

Law of conservation of mass

Mass of products = mass of reactants