NDA Chemistry · Acids, Bases and Salts

Salts and Common Compounds

The household name↔formula table for the common salts (washing soda, baking soda, bleaching powder, gypsum, brine), what is manufactured from common salt, and the properties of bleaching powder.

All Acids, Bases and Salts notes NDA Chemistry strategy

Why this matters

Seven PYQs of name↔formula↔use recall plus two trap questions ('which is NOT made from common salt', 'which statement about bleaching powder is wrong'). The match-list question recurs almost verbatim — learn the four-way table and it is a guaranteed mark.

Concept 1 of 3

Common names and formulas of salts

Intuition

Every Indian entrance exam keeps a short list of household salts with their 'kitchen' name, chemical name and formula. The bank tests any column — give the name, ask the formula, or run a four-way match-list. Learn all three columns for each.

Definition

The high-frequency name↔formula facts:

Washing soda = Na2CO3·10H2O (sodium carbonate decahydrate).
Baking soda = NaHCO3 (sodium bicarbonate).
Bleaching powder = CaOCl2 (calcium oxychloride, also written Ca(OCl)Cl).
Gypsum = CaSO4·2H2O.
Brine = an aqueous solution of NaCl (common salt in water).
Milk of magnesia = Mg(OH)2 (magnesium hydroxide) — an antacid.
Limestone / Chalk / Marble = CaCO3. (Lime water is Ca(OH)2 solution — NOT CaCO3.)

Common name	Chemical name / formula
Washing soda	Sodium carbonate, Na2CO3·10H2OQ
Baking soda	Sodium bicarbonate, NaHCO3
Bleaching powder	Calcium oxychloride, CaOCl2
Gypsum	Calcium sulphate dihydrate, CaSO4·2H2O
Brine	Aqueous solution of NaCl (common salt) Brine is NaCl in water — not NaOH, NaHCO3 or Na2CO3.
Milk of magnesia	Magnesium hydroxide, Mg(OH)2
Lime water	Calcium hydroxide solution, Ca(OH)2 Lime water is Ca(OH)2 — it does NOT represent calcium carbonate. Limestone, chalk and marble are the CaCO3 ones.

Practice this conceptself-check · 6 quick reps

Try it yourself

Match each common name to its formula: Washing soda, Baking soda, Bleaching powder, Gypsum.

Practice — Level 1 (6 reps)

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

1.
Chemical formula of washing soda?
2.
Chemical formula of baking soda?
3.
Chemical formula of bleaching powder?
4.
Brine is an aqueous solution of which compound?
5.
Milk of magnesia is which compound?
6.
Which does NOT represent calcium carbonate: lime water, limestone, chalk or marble?

From the bank · past-year question

Example 1Acids, Bases and SaltsEASY

Brine is an aqueous solution of

[Q66 · Apr · 2018]

Lime water is Ca(OH)2, not CaCO3

Limestone, chalk and marble are all calcium carbonate (CaCO3). Lime water is the odd one out — it is a solution of calcium hydroxide, Ca(OH)2, and does NOT represent calcium carbonate.

Milk of magnesia = Mg(OH)2, not a carbonate

Milk of magnesia is magnesium hydroxide, Mg(OH)2 — an antacid base. It is not magnesium carbonate, bicarbonate or sulphate.

Drill 3 more on common names and formulas of salts

Concept 2 of 3

Compounds manufactured from common salt

Intuition

Common salt (NaCl) is the feedstock for a whole family of sodium and chlorine chemicals — washing soda, baking soda and bleaching powder all trace back to NaCl. The bank's trap is plaster of Paris, which comes from gypsum, not salt.

Definition

What is and is not made from NaCl:

From NaCl (via the Solvay or chlor-alkali process): washing soda (Na2CO3), baking soda (NaHCO3), bleaching powder, NaOH and chlorine.
NOT from NaCl: Plaster of Paris — it is made from gypsum (CaSO4·2H2O), a calcium compound, not a sodium one.

Compound	Made from common salt?	Actual source
Washing soda (Na2CO3)	Yes	NaCl, via Solvay process
Baking soda (NaHCO3)	Yes	NaCl, via Solvay process
Bleaching powder	Yes	Chlorine (from NaCl) + slaked lime
Plaster of Paris	No	Gypsum (CaSO4·2H2O) Plaster of Paris is the trap — it is made from gypsum, NOT from common salt.

Practice this concept3 quick reps

Practice — Level 1 (3 reps)

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

1.
Which is NOT made from common salt: bleaching powder, baking soda, plaster of Paris or washing soda?
2.
Name two compounds manufactured from common salt.
3.
Plaster of Paris is made from which raw material?

From the bank · past-year question

Example 2Acids, Bases and SaltsMODERATE

Common salt (

\text{NaCl}

) is not used as a raw material for preparation of which one of the following compounds ?

[Q100 · Apr · 2021]

Plaster of Paris comes from gypsum, not salt

Washing soda, baking soda and bleaching powder all start from NaCl. Plaster of Paris is the exception — it is made by heating gypsum (CaSO4·2H2O), a calcium mineral, so it is NOT a product of common salt.

Concept 3 of 3

Bleaching powder: formula, uses and properties

Intuition

Bleaching powder (CaOCl2) is an oxidising agent that releases chlorine. Its jobs all rely on that: bleaching paper and textiles, and disinfecting water. The classic trap calls it a reducing agent — it is an OXIDISING agent.

Definition

Bleaching powder facts:

Formula CaOCl2 (calcium oxychloride); it is an oxidising agent, not a reducing agent.
Uses: bleaching wood pulp in paper factories, bleaching linen/cotton in textiles, and disinfecting drinking water.
Bleaching powder and DDT share one feature: both contain chlorine (bleaching powder is inorganic; DDT is organic).

Property / use	Detail
Chemical nature	Oxidising agent (NOT reducing) The bank's wrong statement is 'bleaching powder is a reducing agent' — it is an oxidising agent.
Use 1	Bleaching wood pulp in paper factories
Use 2	Bleaching linen and cotton in textiles
Use 3	Disinfecting drinking water
Shared with DDT	Both contain chlorine Bleaching powder and DDT both contain chlorine — bleaching powder is inorganic, DDT is organic.

Practice this concept4 quick reps

Practice — Level 1 (4 reps)

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

1.
Is bleaching powder an oxidising agent or a reducing agent?
2.
What feature do bleaching powder and DDT have in common?
3.
Name one use of bleaching powder besides bleaching textiles.
4.
Chemical formula of bleaching powder?

From the bank · past-year question

Example 3Acids, Bases and SaltsMODERATE

Which one of the following is NOT true for bleaching powder?

[Q68 · Apr · 2018]

Bleaching powder oxidises, it does not reduce

The statement 'bleaching powder is used as a reducing agent' is NOT true — bleaching powder is an oxidising agent (it releases chlorine). Its bleaching and disinfecting actions are oxidation.

Bleaching powder and DDT share chlorine, not calcium

The correct shared fact is that both contain chlorine. They do NOT both contain calcium (DDT has none), and they are not both organic (bleaching powder is inorganic) or both inorganic (DDT is organic).

Drill 1 more on bleaching powder: formula, uses and properties

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 names and formulas of salts7 rows

Common name	Chemical name / formula
Washing soda	Sodium carbonate, Na2CO3·10H2OQ
Baking soda	Sodium bicarbonate, NaHCO3
Bleaching powder	Calcium oxychloride, CaOCl2
Gypsum	Calcium sulphate dihydrate, CaSO4·2H2O
Brine	Aqueous solution of NaCl (common salt) Brine is NaCl in water — not NaOH, NaHCO3 or Na2CO3.
Milk of magnesia	Magnesium hydroxide, Mg(OH)2
Lime water	Calcium hydroxide solution, Ca(OH)2 Lime water is Ca(OH)2 — it does NOT represent calcium carbonate. Limestone, chalk and marble are the CaCO3 ones.

Compounds manufactured from common salt4 rows

Compound	Made from common salt?	Actual source
Washing soda (Na2CO3)	Yes	NaCl, via Solvay process
Baking soda (NaHCO3)	Yes	NaCl, via Solvay process
Bleaching powder	Yes	Chlorine (from NaCl) + slaked lime
Plaster of Paris	No	Gypsum (CaSO4·2H2O) Plaster of Paris is the trap — it is made from gypsum, NOT from common salt.

Bleaching powder: formula, uses and properties5 rows

Property / use	Detail
Chemical nature	Oxidising agent (NOT reducing) The bank's wrong statement is 'bleaching powder is a reducing agent' — it is an oxidising agent.
Use 1	Bleaching wood pulp in paper factories
Use 2	Bleaching linen and cotton in textiles
Use 3	Disinfecting drinking water
Shared with DDT	Both contain chlorine Bleaching powder and DDT both contain chlorine — bleaching powder is inorganic, DDT is organic.

Watch out for (5)

Lime water is Ca(OH)2, not CaCO3
→ Common names and formulas of salts
Milk of magnesia = Mg(OH)2, not a carbonate
→ Common names and formulas of salts
Plaster of Paris comes from gypsum, not salt
→ Compounds manufactured from common salt
Bleaching powder oxidises, it does not reduce
→ Bleaching powder: formula, uses and properties
Bleaching powder and DDT share chlorine, not calcium
→ Bleaching powder: formula, uses and properties

Mastery check — 4 interleaved questions

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

Example 1Acids, Bases and SaltsEASY

Which one of the following does

\textbf{\text{not}}

represent the salt, Calcium carbonate?

[Q73 · Sep · 2019]

Example 2Acids, Bases and SaltsMODERATE

Which one of the following statements regarding Bleaching powder and D.D.T. is correct?

[Q146 · Apr · 2020]

Example 3Acids, Bases and SaltsMODERATE

Match List I with List II and select the answer using the code given below the Lists : A. Washing soda | 1.

\text{CaOCl}_2

B. Baking soda | 2.

\text{NaHCO}_3

C. Bleaching powder | 3.

\text{Na}_2\text{CO}_3\cdot10\text{H}_2\text{O}

D. Gypsum | 4.

\text{CaSO}_4\cdot2\text{H}_2\text{O}

[Q81 · Apr · 2025]

Example 4Acids, Bases and SaltsEASY

Which one among the following is known as Milk of Magnesia ?

[Q104 · Apr · 2024]

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