Chemistry

Vinegar is a common household liquid used in cooking, cleaning, and food preservation. Understanding its chemical nature is important.

• Chemical Composition:

• Vinegar is typically 4–8% acetic acid (CH₃COOH) dissolved in water.
• The remaining 92–96% is water along with trace amounts of flavoring compounds.

• Acidic Nature:

• Acetic acid gives vinegar its sour taste and characteristic pungent smell.
• The pH of vinegar ranges from 2.5 to 3.5, making it acidic.
• It turns blue litmus paper red, confirming its acidic property.

• Uses as an Acidic Re-agent:

• Cooking: Adds sour flavor to foods, used in pickling (preservation)
• Cleaning: Dissolves mineral deposits, grease, and some stains due to acidity
• Laboratory: Used as a mild acid in various experiments
• Traditional medicine: Sometimes used as a mild disinfectant

Why Other Options are Incorrect:

• (B) Alkaline re-agent: Incorrect. Alkaline substances have pH above 7 (e.g., baking soda, bleach). Vinegar is acidic, not alkaline.
• (C) Greasy solvent: While vinegar can help cut through grease to some extent, this is not its primary classification. “Greasy solvent” is not a standard chemical term, and vinegar is not primarily a solvent for grease (degreasers are usually alkaline).
• (D) Greasy absorbent: Incorrect. Vinegar does not absorb grease; it may help dissolve or remove it through chemical action, but “absorbent” is not an accurate description.

Final Answer: (A) Acidic re-agent

Water is one of the most essential and abundant compounds on Earth. Its molecular formula represents the number and type of atoms in one molecule.

Composition: Water consists of two hydrogen atoms bonded to one oxygen atom.
Formula: H₂O — The subscript "2" indicates two hydrogen atoms, and no subscript after O means one oxygen atom.
Chemical Name: Dihydrogen monoxide (though rarely used in common language).
Molecular Weight: 18.015 g/mol (approximately 18 g/mol).

Why Other Options are Incorrect:

• (B) H₂O₂: This is hydrogen peroxide, a different compound used as a disinfectant and bleaching agent.
• (C) HO₂: This is hydroperoxyl radical, an unstable free radical, not water.
• (D) H₂O₃: This is trioxidane or hydrogen trioxide, an unstable molecule, not water.

Final Answer: (A) H₂O