Acids, Bases, Ionic Equations & pH – Review Flashcards

42 question-and-answer flashcards summarising key definitions, reactions, tests, equations, pH concepts, indicator use, oxide classification and soil pH control from the Acids & Bases lecture notes.

What ion do all acids produce in aqueous solution?

Hydrogen ions, H⁺(aq).

What ion characterises an alkali in aqueous solution?

Hydroxide ions, OH⁻(aq).

How does a strong acid differ from a weak acid?

A strong acid ionises completely in water; a weak acid ionises only partially.

What is the ionic equation for neutralisation between an acid and an alkali?

H⁺(aq) + OH⁻(aq) → H₂O(l)

What colour does Universal Indicator show at pH 7?

Green.

Which indicator changes from red to yellow between pH 3.1 and 4.4?

Methyl orange.

What happens to damp blue litmus paper in an acidic solution?

It turns red.

How do you test for carbon dioxide gas?

Bubble the gas into limewater; a white precipitate forms.

What is the positive test for hydrogen gas?

A lighted splint extinguishes with a ‘pop’ sound.

What are the products of an acid reacting with a metal carbonate?

Salt, water, and carbon dioxide.

What name is given to the reaction ‘acid + base → salt + water’?

Neutralisation.

Why can acids conduct electricity?

Their aqueous solutions contain mobile ions (e.g. H⁺, anions).

Define a base according to the notes.

A metal oxide or hydroxide (generally insoluble) that reacts with acids to form salt and water.

Define an alkali.

A soluble base that produces OH⁻ ions in water.

Give the dissociation equation of sodium hydroxide in water.

NaOH(aq) → Na⁺(aq) + OH⁻(aq).

Give the ionisation equation of ethanoic acid in water.

CH₃COOH(aq) ⇌ CH₃COO⁻(aq) + H⁺(aq).

Name one common weak acid mentioned.

Ethanoic acid (others: carbonic, citric, oxalic, boric).

Why does solid acid show no effect on litmus paper?

Without water it does not produce H⁺ ions, so litmus colour is unchanged.

Name two amphoteric oxides listed in the notes.

Zinc oxide (ZnO) and aluminium oxide (Al₂O₃).

How does metallic character help classify oxides?

Metal oxides are usually basic; non-metal oxides are usually acidic; some metal oxides (e.g. ZnO, Al₂O₃) are amphoteric; some non-metal monoxides (e.g. CO, NO) are neutral.

Why is calcium hydroxide preferred to sodium hydroxide for liming acidic soil?

Ca(OH)₂ is only sparingly soluble, so it raises soil pH more gently and is less likely to make the soil excessively alkaline.

What happens if excess alkali is added to soil containing ammonium sulfate fertiliser?

The alkali reacts to release ammonia gas, reducing available nitrogen for plants.

What is the general solubility of all nitrates in water?

All nitrates are soluble.

Name one insoluble sulfate mentioned.

Barium sulfate (others: calcium sulfate, lead(II) sulfate).

Which chlorides are insoluble in water?

Silver chloride and lead(II) chloride.

Write the ionic equation for the reaction of AgNO₃(aq) with NaCl(aq).

Ag⁺(aq) + Cl⁻(aq) → AgCl(s).

What are spectator ions?

Ions present on both sides of a full ionic equation that do not take part in the reaction.

State three characteristic reactions of acids described.

(1) Acid + base/alkali → salt + water; (2) Acid + metal carbonate → salt + water + CO₂; (3) Acid + reactive metal → salt + H₂.

How can you experimentally compare reaction rates of strong and weak acids with magnesium ribbon?

Add equal concentrations/volumes of each acid to Mg; measure volume of H₂ produced per unit time (strong acid reacts faster).

What does the ‘basicity’ of an acid mean?

The maximum number of H⁺ ions an acid molecule can produce on ionisation.

What is the basicity of phosphoric acid, H₃PO₄?

Three (tribasic).

Which pH values correspond to strongly acidic solutions?

Approximately pH 0–3.

How is pH mathematically related to hydrogen-ion concentration?

pH = –log₁₀[H⁺].

In a titration curve, what does the steep vertical section signify?

The rapid pH change at the equivalence (end-point) of neutralisation.

What can the initial pH of a titration curve reveal?

The strength (strong or weak) of the acid placed in the flask.

Name a suitable indicator for a strong acid–strong alkali titration and why.

Phenolphthalein (or bromothymol blue/methyl orange); it changes colour within the sharp pH rise at equivalence.

Define a salt as used in the notes.

A compound formed when the H⁺ of an acid is replaced by a metal or NH₄⁺ ion.

What products form when an alkali reacts with an ammonium salt on warming?

Salt, water, and ammonia gas.

Give the ionic equation for the reaction between NaOH(aq) and NH₄⁺(aq).

OH⁻(aq) + NH₄⁺(aq) → H₂O(l) + NH₃(g).

Why must the mixture be warmed in an alkali–ammonium salt reaction?

Heating helps release dissolved ammonia gas so it can be detected.

Write the balanced equation for ZnO reacting with hydrochloric acid.

ZnO(s) + 2HCl(aq) → ZnCl₂(aq) + H₂O(l).

Write the balanced equation for ZnO reacting with sodium hydroxide.

ZnO(s) + 2NaOH(aq) → Na₂ZnO₂(aq) + H₂O(l) (sodium zincate formation).

Why does hydrochloric acid in an organic solvent not react with magnesium ribbon?

Without water it cannot produce H⁺ ions, so no reaction occurs.

How is extent of dissociation linked to electrical conductivity?

Greater ionisation (strong acids/alkalis) provides more mobile ions, so conductivity is higher.

To which oxide class does CO₂ belong?

Acidic oxide.