Flashcards · 0620 · Topic 7

Acids, bases and salts flashcards

21 cards on Topic 7, subtopics 7.1 to 7.3. Pick a subtopic or study them all.

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pH of acidic, neutral and alkaline solutions: Acidic: below 7. Neutral: 7. Alkaline: above 7.
Colours of litmus, methyl orange and thymolphthalein in acid and in alkali: Litmus: red in acid, blue in alkali. Methyl orange: red in acid, yellow in alkali. Thymolphthalein: colourless in acid, blue in alkali.
Which ions do aqueous acids and aqueous alkalis contain?: Acids: H⁺ ions. Alkalis: OH⁻ ions.
Alkali: A soluble base. All alkalis are bases, but not all bases are alkalis.
acid + metal → acid + base → acid + carbonate →: salt + hydrogen salt + water salt + water + carbon dioxide
What is made when an alkali is warmed with an ammonium salt?: Ammonia gas (plus a salt and water).
Acid (proton definition)Extended: A proton (H⁺) donor.
Base (proton definition)Extended: A proton (H⁺) acceptor.
Strong acidExtended: Fully dissociated in water. Examples: HCl, HNO₃, H₂SO₄.
Weak acidExtended: Only partially dissociated in water. Examples: ethanoic, citric and carbonic acids.

Acidic oxides: Oxides of non-metals, such as SO₂ and CO₂. They react with bases and alkalis.
Basic oxides: Oxides of metals, such as CuO and CaO. They react with acids.
Amphoteric oxidesExtended: Oxides that react with both acids and bases to form a salt and water. Examples: aluminium oxide, Al₂O₃, and zinc oxide, ZnO.

Making a soluble salt from an acid and an insoluble base (or carbonate or metal): Add the solid in excess to the acid, filter off the leftover solid, then crystallise the filtrate.
When is titration used to make a salt?: When both reactants are soluble (acid + alkali), so there is no excess solid to filter off. Repeat without the indicator to get a pure salt.
Which common salts are always soluble?: All sodium, potassium and ammonium salts, and all nitrates.
Exceptions to the solubility rules for chlorides and sulfates: Chlorides: soluble except silver and lead. Sulfates: soluble except barium, calcium and lead.
Solubility of carbonates and hydroxides: Mostly insoluble, except sodium, potassium and ammonium (calcium hydroxide is partially soluble).
Hydrated and anhydrous: Hydrated: a substance chemically combined with water (e.g. CuSO₄·5H₂O). Anhydrous: containing no water.
Making an insoluble saltExtended: Precipitation: mix two solutions containing its ions, then filter, wash the precipitate with distilled water and dry it.
Water of crystallisationExtended: The water molecules chemically combined within the crystal structure of a hydrated salt.