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.

All Carbon and Its Compounds notes NDA Chemistry strategy

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

Intuition

The functional group is the small cluster of atoms that gives an organic molecule its character. Swap the group and you change the family — an -OH makes an alcohol, a -COOH makes an acid, a -COO- makes a sweet-smelling ester.

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

Practice — Level 1 (5 reps)

Quick reps to lock in the method. Try each, then check.

1.
Which family of compounds has a sweet, fruity smell?
2.
What is the functional group of an alcohol?
3.
What is the action of litmus on ethanol?
4.
Which acid is present in a nettle sting?
5.
Is acetic acid organic or inorganic?

From the bank · past-year question

Example 1Carbon and Its CompoundsEASY

Which one among the following compounds has a sweet and fruity smell ?

[Q101 · Apr · 2024]

Alcohol is neutral, acid turns litmus red

Ethanol (an alcohol) is neutral to litmus. Only the -COOH acids (acetic, formic) turn blue litmus red. Options that say ethanol turns litmus red are wrong.

Drill 3 more on functional groups and their families

Concept 2 of 3

Carbon monoxide and other named facts

Intuition

A cluster of one-off recall facts the bank repeats: why carbon monoxide kills, where litmus comes from, and that carbon tops the periodic table for sheer number of compounds.

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

Practice — Level 1 (3 reps)

Quick reps to lock in the method. Try each, then check.

1.
Why is carbon monoxide poisonous?
2.
Litmus is derived from which organism?
3.
Which element forms the highest number of compounds?

From the bank · past-year question

Example 2Carbon and Its CompoundsEASY

The Poisonous nature of Carbon monoxide (

\text{CO}

) is due to its

[Q88 · Apr · 2018]

Drill 2 more on carbon monoxide and other named facts

Concept 3 of 3

Common compounds — formula and use

Intuition

A short formula-recall block: baking soda's decomposition is why cakes rise, and gypsum's formula carries its two waters of crystallization.

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

Practice — Level 1 (3 reps)

Quick reps to lock in the method. Try each, then check.

1.
Chemical formula of baking soda?
2.
Which gas released by baking soda makes cakes rise?
3.
Chemical formula of gypsum?

From the bank · past-year question

Example 3Carbon and Its CompoundsMODERATE

At nearly 70°C, sodium bicarbonate shows the property of gradually decomposing, which makes it usable in bakery products. The product of decomposition responsible for this use of sodium bicarbonate is

[Q143 · Apr · 2020]

Drill 1 more on common compounds — formula and use

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

Mastery check — 5 interleaved questions

Try each one before clicking. Questions are interleaved across the concepts above, not grouped — interleaving sharpens transfer.

Example 1Carbon and Its CompoundsEASY

Which one among the following is present in the nettle leaf hairs that causes burning pain ?

[Q103 · Apr · 2024]

Example 2Carbon and Its CompoundsEASY

Which one of the following elements forms highest number of compounds ?

[Q90 · Apr · 2017]

Example 3Carbon and Its CompoundsEASY

Which one of the following is the chemical formula of gypsum?

[Q106 · Sep · 2018]

Example 4Carbon and Its CompoundsEASY

Which one of the following is an organic acid?

[Q83 · Apr · 2019]

Example 5Carbon and Its CompoundsEASY

Litmus, a well-known acid-base indicator, is derived from :

[Q66 · Apr · 2024]

Drill every past-year question on this subtopic

9 questions from the bank — paginated, with cart and Word-export support.

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