NDA Chemistry · Industrial and Applied Chemistry
Common Industrial Substances and Alloys
The composition of everyday industrial substances and alloys — plaster of Paris, borax, soft soap and solder — plus the raw materials of Portland cement, all answered by knowing one formula or element list per item.
Why this matters
Five PYQs of pure composition recall. The bank asks 'solder is an alloy of...', 'the formula of plaster of Paris is...', or 'soft soap contains...'. Each is a single fact: solder = Pb + Sn, plaster of Paris = CaSO₄·½H₂O, soft soap = potassium soap, borax = Na, B, O, H.
Concept 1 of 3: Common alloys and their composition
Definition
The alloy composition facts:
- Solder = lead (Pb) + tin (Sn) — a low-melting alloy for joining metals.
- Brass = copper (Cu) + zinc (Zn).
- Bronze = copper (Cu) + tin (Sn).
- Steel = iron (Fe) + carbon (C).
- Duralumin = aluminium (Al) + copper (Cu) + magnesium + manganese.
| Alloy | Composition | Use |
|---|---|---|
| Solder | Lead (Pb) + tin (Sn) | Joining/soldering metals Solder is an alloy of lead and tin (Pb + Sn). |
| Brass | Copper + zinc (Cu + Zn) | Fittings, instruments |
| Bronze | Copper + tin (Cu + Sn) | Statues, coins, bearings |
| Steel | Iron + carbon (Fe + C) | Construction, tools |
| Duralumin | Al + Cu + Mg + Mn | Aircraft (light, strong) |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Industrial and Applied Chemistry · Common Industrial Substances and Alloys
Solder = Pb + Sn, brass = Cu + Zn, bronze = Cu + Sn
Concept 2 of 3: Plaster of Paris, borax and soft soap
Definition
The named-substance facts:
- Plaster of Paris = CaSO₄·½H₂O (calcium sulphate hemihydrate), made by heating gypsum. Sets hard when mixed with water.
- Borax is composed of sodium, boron, oxygen and hydrogen (Na₂B₄O₇·10H₂O).
- Soft soap is a potassium soap — it contains potassium (hard soap is the sodium salt). Soft soap is more soluble and used in liquid/shaving soaps.
| Substance | Formula / composition | Key fact |
|---|---|---|
| Plaster of Paris | CaSO₄·½H₂O | Calcium sulphate hemihydrate; from gypsum Plaster of Paris = CaSO₄·½H₂O (½ water per CaSO₄), not CaSO₄·2H₂O (that is gypsum). |
| Borax | Na, B, O, H (Na₂B₄O₇·10H₂O) | Sodium tetraborate decahydrate Borax contains sodium, boron, oxygen and hydrogen. |
| Soft soap | Potassium soap | Contains potassium (K) Soft soap = potassium salt; HARD soap = sodium salt. |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 2 · Industrial and Applied Chemistry · Common Industrial Substances and Alloys
Soft soap = potassium, hard soap = sodium
Plaster of Paris is ½ water, gypsum is 2 waters
Concept 3 of 3: Raw materials of Portland cement
Definition
The raw materials of Portland cement:
- Lime (CaO) — from limestone / calcium carbonate.
- Silica (SiO₂) — from clay or sand.
- Alumina (Al₂O₃) — from clay.
- Plus a little iron oxide. A small amount of gypsum is added at the end to control setting time.
| Raw material | Provides | Source |
|---|---|---|
| Limestone | Lime (CaO) | Calcium carbonate rock |
| Clay / sand | Silica (SiO₂) | Clay, sand |
| Clay | Alumina (Al₂O₃) | Aluminosilicate clay |
| Iron ore + gypsum | Iron oxide; setting control | Added in small amounts Lime, silica and alumina are the essential trio — gypsum is only a setting regulator. |
Practice this concept3 quick reps
The same idea in a real exam question:
Example 3 · Industrial and Applied Chemistry · Common Industrial Substances and Alloys
Lime + silica + alumina is the trio
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)
Common alloys and their composition5 rows
| Alloy | Composition | Use |
|---|---|---|
| Solder | Lead (Pb) + tin (Sn) | Joining/soldering metals Solder is an alloy of lead and tin (Pb + Sn). |
| Brass | Copper + zinc (Cu + Zn) | Fittings, instruments |
| Bronze | Copper + tin (Cu + Sn) | Statues, coins, bearings |
| Steel | Iron + carbon (Fe + C) | Construction, tools |
| Duralumin | Al + Cu + Mg + Mn | Aircraft (light, strong) |
Plaster of Paris, borax and soft soap3 rows
| Substance | Formula / composition | Key fact |
|---|---|---|
| Plaster of Paris | CaSO₄·½H₂O | Calcium sulphate hemihydrate; from gypsum Plaster of Paris = CaSO₄·½H₂O (½ water per CaSO₄), not CaSO₄·2H₂O (that is gypsum). |
| Borax | Na, B, O, H (Na₂B₄O₇·10H₂O) | Sodium tetraborate decahydrate Borax contains sodium, boron, oxygen and hydrogen. |
| Soft soap | Potassium soap | Contains potassium (K) Soft soap = potassium salt; HARD soap = sodium salt. |
Raw materials of Portland cement4 rows
| Raw material | Provides | Source |
|---|---|---|
| Limestone | Lime (CaO) | Calcium carbonate rock |
| Clay / sand | Silica (SiO₂) | Clay, sand |
| Clay | Alumina (Al₂O₃) | Aluminosilicate clay |
| Iron ore + gypsum | Iron oxide; setting control | Added in small amounts Lime, silica and alumina are the essential trio — gypsum is only a setting regulator. |
Watch out for (4)
- Solder = Pb + Sn, brass = Cu + Zn, bronze = Cu + Sn→ Common alloys and their composition
- Soft soap = potassium, hard soap = sodium→ Plaster of Paris, borax and soft soap
- Plaster of Paris is ½ water, gypsum is 2 waters→ Plaster of Paris, borax and soft soap
- Lime + silica + alumina is the trio→ Raw materials of Portland cement
Test yourself on Industrial and Applied Chemistry
10 past NDA questions from this chapter, timed at 10 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.