Kitchen Chemistry: Formulas & Names

The CGL Trap:
The examiner asks for the formula of "Blue Vitriol". You know it's Copper Sulfate, but is it $5H_2O$ or $10H_2O$?
Chemistry in competitive exams is less about reactions and more about Common Names vs. Chemical Names.

1. The "Soda" Confusion

The biggest source of negative marks. Remember: "Bi" means Buy (You buy food to cook, so Bicarbonate is for cooking).

Baking Soda NaHCO₃ Sodium Bicarbonate Used in cakes (makes them fluffy) and Fire Extinguishers.

Washing Soda Na₂CO₃·10H₂O Sodium Carbonate Decahydrate Used to remove permanent hardness of water.

Caustic Soda NaOH Sodium Hydroxide Used in making Soap and Paper. Strong Base.

2. The "Lime" Cycle

Calcium changes its name every time you add water or air to it.

Quick Lime CaO Calcium Oxide Pure lime. Used in cement manufacturing.

Slaked Lime Ca(OH)₂ Calcium Hydroxide Formed when water is added to Quick Lime (White washing).

Limestone / Chalk CaCO₃ Calcium Carbonate Marble, Eggshells, and Pearls are made of this.

3. The "Acid" Attack

One question on "Natural Acids" is fixed in almost every shift.

[Image of pH scale examples]

Source	Acid Present
Vinegar	Acetic Acid
Ant/Bee Sting	Formic / Methanoic Acid
Sour Milk / Curd	Lactic Acid
Lemon / Orange	Citric Acid
Tamarind / Grapes	Tartaric Acid
Rancid Butter	Butyric Acid
Tomato / Spinach	Oxalic Acid

4. The Plaster Confusion

The difference between a hard rock (Gypsum) and a plaster cast (POP) is just water.

• Gypsum: $CaSO_4 \cdot 2H_2O$ (Has 2 water molecules).
• Plaster of Paris (POP): $CaSO_4 \cdot \frac{1}{2}H_2O$ (Has half water molecule).
• When you heat Gypsum at 373K, it loses water and becomes POP.

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Revision Flashcards

Bleaching Powder

What is the chemical name?

Calcium Oxychloride

Formula: CaOCl₂. Used for disinfecting water.

Dry Ice

What is it actually?

Solid Carbon Dioxide

Formula: CO₂ (Solid). It sublimates directly from solid to gas.

Laughing Gas

Formula?

Nitrous Oxide

Formula: N₂O. Used as an anesthetic by dentists.

Aqua Regia

What is the mixture?

HCl + HNO₃

Concentrated Hydrochloric and Nitric acid in a ratio of 3:1. It dissolves Gold.

Exam-Style MCQs

Q1. What is the chemical formula of "Blue Vitriol"?

A) FeSO₄·7H₂O

B) CuSO₄·5H₂O

Correct! Copper Sulfate Pentahydrate is Blue. (FeSO₄ is Green Vitriol).

C) ZnSO₄·7H₂O

Q2. Which acid is present in Tomato?

A) Tartaric Acid

B) Oxalic Acid

Correct! Oxalic acid is found in Tomatoes and Spinach (and kidney stones).

C) Acetic Acid

Q3. "Milk of Magnesia" is chemically known as:

A) Magnesium Hydroxide

Correct! Mg(OH)₂. It is used as an antacid to cure acidity.

B) Magnesium Carbonate

C) Magnesium Oxide

Part of the CGL Science Series.