Acids and Bases
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50 free Acids and Bases trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Acids and bases are the chemistry you can taste, smell and spill. They sour your food, clean your kitchen, start your car and keep your body running, and the gap between a harmless one and a dangerous one often comes down to a single number on a scale. This quiz covers the ground a chemistry class does: which acids and bases are strong and which are weak, what the pH scale really measures, how indicators change colour, what happens when an acid meets a base, and the salts that result. It also strays into kitchens, gardens, medicine cabinets and other planets, where the same reactions turn up in surprising places. It is pitched for high school students revising for a test, teachers who want a ready-made worksheet, and anyone curious about how much they still know. Every answer comes with a short explanation, so you learn something even when you guess wrong.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Which of these acids, sprayed by ants to defend their nests, is named after the Latin for 'ant'?
Formic acid
Formic acid takes its name from formica, the Latin for ant. English naturalist John Ray first isolated it in 1671 by distilling large numbers of the insects.
Q 02Which alchemists' mixture of two acids can dissolve gold, although neither acid manages it alone?
Aqua regia
Aqua regia once hid two Nobel medals: in wartime Copenhagen, George de Hevesy dissolved them in it to keep the gold from the Nazis, then recovered the metal after the war.
Q 03Søren Sørensen devised the pH scale while he was head of the research laboratory of which brewery?
Carlsberg
Carlsberg employed Sørensen to study how hydrogen ions affect proteins, and he wanted a simple way to express their concentration. The same laboratory isolated the yeast behind lager.
Q 04Which vegetable's juice is a homemade pH indicator, pink in acids and yellow in strong bases?
Red cabbage
Red cabbage owes the trick to its anthocyanin pigment, which is magenta in acids, purple at the midpoint and shifts through blue towards yellow as a solution turns more basic.
Q 05Which garden shrub acts as a living pH test, blooming blue in acidic soil and pink in alkaline soil?
Hydrangea
Hydrangea flowers turn blue only when acidic soil frees aluminium ions for the roots to absorb. Alkaline ground ties the metal up, so the same plant blooms pink.
Q 06Which baked snack gets its dark, glossy crust from a quick bath in lye before it goes in the oven?
Pretzels
Pretzels get their traditional skin and flavour from the Maillard browning reaction, which the strongly basic dip sets off on the surface of the dough.
Q 07Which element did Antoine Lavoisier name 'acid-maker', wrongly believing it was part of every acid?
Oxygen
Oxygen comes from Greek roots meaning 'acid producer'. The mistake surfaced when some strong acids proved to contain none of it, but by then the name had stuck.
Q 08Which of these acids, additive E338 on labels, gives Coca-Cola and other colas their sharp tang?
Phosphoric acid
Phosphoric acid is why such drinks are sometimes called phosphate sodas, or simply phosphates. It also has the potential to erode teeth.
Q 09Which stone, used for classical statues and the Parthenon, is steadily eaten away by acid rain?
Marble
Marble reacts with acids so readily that vinegar is ruled out for cleaning it, and Harvard wraps some of its outdoor marble statues in waterproof covers every winter.
Q 10Which of these protein-rich kitchen staples is naturally alkaline rather than acidic?
Egg white
Egg white is an alkaline solution, about 90% water with the rest mostly proteins such as albumins and globulins dissolved in it.
Q 11Which of the strong acids, known to alchemists as spirits of salt, is also made by the human stomach lining?
Hydrochloric acid
Hydrochloric acid brings the stomach's contents down to about pH 1 to 2, a barrier against swallowed microbes. The stomach shields itself behind a thick layer of mucus.
Q 12Which of the strong acids makes up the permanent clouds of Venus and is the electrolyte in car batteries?
Sulfuric acid
Sulfuric acid is so central to manufacturing that a nation's output of it was long treated as a measure of its industrial strength. Most of it goes into fertiliser.
Q 13Which of the weak acids, diluted in water, gives vinegar its sour taste and pungent smell?
Acetic acid
Q 21Which strong base, commonly called lye, is used to make hard bar soap and to unblock drains?
Sodium hydroxide
Sodium hydroxide clears a blocked pipe by converting the fat and grease into soap, which then dissolves in water.
Q 22Which pungent gas, a weak base, is dissolved in water to make many household glass cleaners?
Ammonia
Ammonia is also the vapour released by smelling salts, where its sharp, irritating odour works as a respiratory stimulant.
Q 23Which kitchen powder, a mild base, foams up with vinegar in the classic school volcano experiment?
Baking soda
Baking soda foams because the reaction releases a gas, and the same bubbles make cakes rise when the powder meets an acid in the batter.
Acetic acid was probably the first acid people ever made in bulk, because vinegar has been produced since the third millennium BCE.
Q 14Which of these acids, the sour note in oranges and limes, is now made mostly by feeding sugar to a mould?
Citric acid
Citric acid switched from fruit to fermentation after World War I disrupted Italian fruit exports. Cultures of the black mould Aspergillus niger are still the main industrial route.
Q 15Which of these acids, made by bacteria fermenting sugars, gives yoghurt and sauerkraut their sour tang?
Lactic acid
Lactic acid does two jobs in fermented foods: it supplies the sourness and it makes them keep, which is why sauerkraut has such a long shelf life.
Q 16Which of the weak acids, made when the gas in fizzy drinks dissolves, also makes clean rain slightly acidic?
Carbonic acid
Carbonic acid is the reason unpolluted rain still has a pH below 7. It is also unstable, constantly breaking back down into water and gas.
Q 17Which of these acids attacks glass so readily that it has to be stored in plastic containers?
Hydrofluoric acid
Hydrofluoric acid counts as a weak acid in dilute solution, yet it is dangerous to handle because it attacks the calcium in bones.
Q 18Which of the strong acids stains human skin yellow on contact and is used mainly to make fertilisers?
Nitric acid
Nitric acid turns skin yellow by reacting with keratin, the protein in skin and nails. Jewellers use a drop of it to show up low-carat alloys.
Q 19Which of these acids helps make rhubarb leaves poisonous, although the plant's stalks are safe to eat?
Oxalic acid
Oxalic acid caused real poisonings in Britain during World War I, when rhubarb leaves were mistakenly recommended as a food.
Q 20Ascorbic acid, a name coined to mean 'without scurvy', is the chemical name of which essential nutrient?
Vitamin C
Vitamin C is something most animals make for themselves. Humans, other higher primates and guinea pigs carry a broken gene for it, so they have to get it from food.
Q 24Which over-the-counter remedies, such as Tums, relieve heartburn by raising the pH inside the stomach?
Antacids
Antacids simply cancel out what is already in the stomach. Unlike acid-reducing drugs, they do nothing to stop more being made.
Q 25Which crushed rock do farmers and gardeners spread on acidic soil to raise its pH?
Limestone
Limestone reacts as a base in the ground. For the same reason, lakes that sit on it stay less acidic under polluted rain than lakes on silicate rock.
Q 26Before industrial chemistry, soap-makers got their alkali by soaking which material in water?
Wood ash
Wood ash was soaked in water and the liquid boiled dry in large iron pots, leaving a pale residue that became known as pot ash.
Q 27Alkaline batteries take their name from their electrolyte, which is a solution of which strong base?
Potassium hydroxide
Potassium hydroxide is the caustic liquid that seeps out when old cells leak, irritating skin and eyes, which is why batteries are best removed from devices going into storage.
Q 28Acids taste sour, but which taste is typical of bases, which also feel slippery to the touch?
Bitter
Bitter is the taste, and the slippery feel has an unnerving cause: a strong base starts turning the natural oils on skin into soap.
Q 29Which Surrey town, home of the Derby horse race, gave its name to the bath salt magnesium sulfate?
Epsom
Epsom drew crowds in the 17th century to a spring on its common, whose mineral-rich water was believed to have healing qualities.
Q 30Which crop is cooked in an alkaline solution, a step called nixtamalisation, before being ground for tortillas?
Maize
Maize cooked this way softens, sheds its hulls and gives up nutrients that help prevent pellagra, a deficiency disease.