NDA Chemistry · Carbon and Its Compounds
Functional Groups and Common Organic Compounds
A functional group is the reactive part of an organic molecule that decides its family and properties — alcohols, acids, esters — plus a handful of named compounds the bank tests on sight.
Why this matters
Nine PYQs of pure recall: which group gives a fruity smell (ester), which acid is in a nettle sting (formic), why carbon monoxide is poisonous, and a few common formulas. Learn the group→family→property table and the named facts; there is nothing to derive.
Concept 1 of 3: Functional groups and their families
Definition
The families the bank tests, with their group and a giveaway property:
- Alcohol — group -OH — e.g. ethanol; neutral to litmus (does not turn litmus red).
- Carboxylic acid — group -COOH — e.g. acetic acid (ethanoic), formic acid (methanoic); sour, turns blue litmus red.
- Ester — group -COO- — e.g. ethyl acetate; sweet, fruity smell (used in flavourings).
- Aldehyde / ketone — groups -CHO / C=O — e.g. formaldehyde, acetone.
| Family | Functional group | Example | Giveaway property |
|---|---|---|---|
| Alcohol | -OH | Ethanol | Neutral to litmus Ethanol does NOT turn litmus red — alcohols are neutral, unlike acids. |
| Carboxylic acid | -COOH | Acetic acid; formic (methanoic) acid | Sour; turns blue litmus red |
| Ester | -COO- | Ethyl acetate | Sweet, fruity smell |
| Aldehyde / Ketone | -CHO / C=O | Formaldehyde / Acetone | Reactive carbonyl group |
Practice this concept5 quick reps
The same idea in a real exam question:
Example 1 · Carbon and Its Compounds · Functional Groups and Common Organic Compounds
Alcohol is neutral, acid turns litmus red
Concept 2 of 3: Carbon monoxide and other named facts
Definition
The recurring named facts:
- Carbon monoxide (CO) is poisonous because it binds haemoglobin (forming carboxyhaemoglobin), blocking oxygen transport. CO is also a neutral oxide.
- Litmus (the acid–base indicator) is extracted from lichens.
- Carbon forms the largest number of compounds of any element (catenation + tetra-valency).
| Fact | Detail |
|---|---|
| CO is poisonous because… | It binds haemoglobin (carboxyhaemoglobin), blocking O₂ transport CO is dangerous because of its affinity for haemoglobin — not because it is acidic. CO is a neutral oxide. |
| Litmus is derived from… | Lichens |
| Element forming the most compounds | Carbon |
Practice this concept3 quick reps
The same idea in a real exam question:
Example 2 · Carbon and Its Compounds · Functional Groups and Common Organic Compounds
Concept 3 of 3: Common compounds — formula and use
Definition
Two high-frequency formulas:
- Baking soda = NaHCO₃ (sodium bicarbonate). On heating above ~70°C it decomposes, releasing CO₂ gas that makes dough rise: 2NaHCO₃ → Na₂CO₃ + H₂O + CO₂.
- Gypsum = CaSO₄·2H₂O (calcium sulphate dihydrate).
| Common name | Formula | Key fact / use |
|---|---|---|
| Baking soda | NaHCO₃ | Decomposes on heating → CO₂ makes cakes rise It is the released CO₂ — not water vapour — that raises the dough. |
| Gypsum | CaSO₄·2H₂O | Two waters of crystallization; used to make plaster of Paris |
Practice this concept3 quick reps
The same idea in a real exam question:
Example 3 · Carbon and Its Compounds · Functional Groups and Common Organic Compounds
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (3)
Functional groups and their families4 rows
| Family | Functional group | Example | Giveaway property |
|---|---|---|---|
| Alcohol | -OH | Ethanol | Neutral to litmus Ethanol does NOT turn litmus red — alcohols are neutral, unlike acids. |
| Carboxylic acid | -COOH | Acetic acid; formic (methanoic) acid | Sour; turns blue litmus red |
| Ester | -COO- | Ethyl acetate | Sweet, fruity smell |
| Aldehyde / Ketone | -CHO / C=O | Formaldehyde / Acetone | Reactive carbonyl group |
Carbon monoxide and other named facts3 rows
| Fact | Detail |
|---|---|
| CO is poisonous because… | It binds haemoglobin (carboxyhaemoglobin), blocking O₂ transport CO is dangerous because of its affinity for haemoglobin — not because it is acidic. CO is a neutral oxide. |
| Litmus is derived from… | Lichens |
| Element forming the most compounds | Carbon |
Common compounds — formula and use2 rows
| Common name | Formula | Key fact / use |
|---|---|---|
| Baking soda | NaHCO₃ | Decomposes on heating → CO₂ makes cakes rise It is the released CO₂ — not water vapour — that raises the dough. |
| Gypsum | CaSO₄·2H₂O | Two waters of crystallization; used to make plaster of Paris |
Watch out for (1)
- Alcohol is neutral, acid turns litmus red→ Functional groups and their families
Test yourself on Carbon and Its Compounds
15 past NDA questions from this chapter, timed at 15 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.