Identify the mineral acid/acids from following acids :
(a) Oxalic acid
(b) Sulphuric acid
(c) Nitric acid
(d) Hydrochloric acid

Question

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Correct — option (2), '(b), (c) and (d)'. Acids are sorted into two families by where they come from and how they are built. Mineral acids, also called inorganic acids, are prepared from mineral sources and have no carboxyl group; the three classical members are sulphuric acid (H2SO4), nitric acid (HNO3) and hydrochloric acid (HCl), and phosphoric acid (H3PO4) is usually added to the list. Organic acids come from plant and animal material and carry the carboxyl group -COOH: acetic acid in vinegar, citric acid in lemon and orange, lactic acid in sour milk, formic acid in the sting of an ant or nettle, tartaric acid in tamarind and grapes, malic acid in apple. Now take the four statements in turn. Statement (a), oxalic acid, has the formula (COOH)2 — two carboxyl groups joined together, the simplest dicarboxylic acid. It occurs naturally in tomato, spinach and wood sorrel, the plant Oxalis from which it takes its name, and it is an organic acid, not a mineral one. Statements (b), (c) and (d) are the three classical mineral acids. So exactly three of the four qualify, and the option that names those three is option (2). The disciplined method here is to classify each statement independently before looking at the option list at all — sort first, then read off the option that matches the sort. Working the other way round, by testing options against half-remembered statements, is how a candidate ends up choosing an option that happens to contain the one acid he is sure about.

Why the other options are wrong — (a) This is the exact inversion of the truth: it names the one organic acid in the list and rejects the three mineral acids. It is the answer a candidate reaches by misreading the stem as 'identify the acid that is not a mineral acid', or by half-remembering that oxalic acid is somehow the odd one out and then attaching that memory to the wrong question. Oxalic acid is indeed the odd one out — which is why it is the one statement that must be excluded, not the one that must be selected. Whenever a question asks you to identify members of a category and one item is conspicuously different, check which way the stem is pointing before you mark.  (c) Hydrochloric acid is certainly a mineral acid, so this option is not wrong about what it contains — it is wrong about what it leaves out. Sulphuric acid and nitric acid are mineral acids on exactly the same footing, and no defensible definition admits HCl while excluding H2SO4 and HNO3. An option of the form 'Only (x)' in a question whose statement list contains three obvious members of the category is asking you to doubt yourself; the cure is to have classified all four before you look at the options, so that a partial option can be discarded on sight.  (d) Sulphuric and nitric acid are correctly included, but hydrochloric acid is dropped for no reason that survives inspection. HCl is a mineral acid by every criterion in use: it is made from inorganic starting materials, it carries no carboxyl group, and it is one of the three strong acids of the school laboratory. It also occurs in the human stomach, where the gastric glands secrete it to give the stomach its acidic medium — a fact that sometimes misleads candidates into filing it as 'biological' and therefore organic. Origin in a living body is not the test; the presence of the carboxyl group and the inorganic constitution of the molecule are.

Concept: The mineral-versus-organic split is a classification by constitution and source rather than by strength. A mineral acid is built entirely from inorganic components; an organic acid is built on a carbon skeleton carrying one or more carboxyl (-COOH) groups, and is characteristically obtained from plant or animal material. Strength is a separate axis altogether and must not be substituted for the classification: hydrochloric, sulphuric and nitric acid are strong, but carbonic acid and boric acid are weak and are still mineral acids, while among organic acids some are weak and a few are very strong. There is also one honest exception to the shortcut 'contains carbon means organic' — carbonic acid, H2CO3, contains a carbon atom and is nonetheless classed as an inorganic acid, because it is simply carbon dioxide dissolved in water and carries no carboxyl group of the organic kind.

State PCS 2026 Q66 — Science & Technology PYQ with Answer

State PCS 2026 Q66 — Science & Technology PYQ with Answer