Basics & Vocabulary
What ion do acids release in water?
H⁺ (hydrogen ions)
What pH is neutral at room temperature?
7
Complete the word equation: acid + metal →
salt + hydrogen
What two products form when hydrochloric acid reacts with sodium hydroxide?
Sodium chloride and water
Name one common household acid and one alkali.
Vinegar (ethanoic acid);
baking soda solution or milk of magnesia (alkali)
A base that is soluble in water and produces OH⁻ (hydroxide ions)
alkali
What colour does blue litmus turn in acid?
Red (and red litmus turns blue in alkali)
What do all acids have in common when dissolved in water?
They all produce hydrogen ions (H⁺), which give acids their characteristic properties such as sour taste and ability to react with metals.
What type of salts are formed from sulfuric acid?
Sulfates (e.g. copper(II) sulfate)
What product is used to relieve indigestion by neutralising stomach acid?
An antacid
Reaction of H⁺ from an acid with OH⁻ from a base to form water (overall: salt + water)
neutralisation
A solution turns universal indicator orange. Is it acidic or alkaline, and roughly what pH range?
Acidic, about pH 3–4
What type of substances do acids react with to produce salt and hydrogen gas?
Metals.
Example: Hydrochloric acid + zinc → zinc chloride + hydrogen.
Predict the salt from nitric acid + potassium hydroxide.
Potassium nitrate
Bee stings are acidic. What simple household substance could help neutralise them?
Baking soda (sodium hydrogencarbonate) paste
(Note: wasp stings are alkaline—vinegar can help.)
A compound (hydroxide or metal oxide) that reacts with both an acid and an alkali to give a salt and water.
amphoteric compound
Name an indicator suitable for a titration between a strong acid and a strong alkali.
Phenolphthalein or methyl orange
Hydrochloric acid reacts with calcium carbonate. Name the salt formed.
Calcium chloride
What two main substances are always formed when an acid reacts with a base?
Salt and water
Why do farmers spread garden lime (calcium carbonate/calcium hydroxide) on acidic soil, and what change in pH is expected?
Lime neutralises soil acidity, so the pH rises toward neutral, improving plant growth.
How is a strong acid different from a weak acid at the same concentration?
Strong acids fully ionise in water (e.g. HCl);
weak acids partially ionise (e.g. ethanoic acid)
Solution A has pH 3, solution B has pH 5. Which is more acidic, and by about how many times?
A is more acidic; about 100× (each pH unit ≈ tenfold change in [H⁺])
Write a balanced symbol equation for nitric acid reacting with sodium hydroxide.
HNO₃ + NaOH → NaNO₃ + H₂O
What is the general word equation for a neutralisation reaction?
Acid + Base → Salt + Water
A kettle has limescale (mainly calcium carbonate). Suggest a safe household method to remove it and explain the chemistry.
Use warm vinegar or citric acid solution; the acid neutralises calcium carbonate to form a soluble calcium salt, water, and carbon dioxide gas (seen as fizzing).