Study Guides/Chemistry/Molecular Weight of NaOH — Sodium Hydroxide
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Molecular Weight of NaOH (Sodium Hydroxide)

The molecular weight (molar mass) of NaOH (sodium hydroxide) is 40 g/mol. Sodium hydroxide is a strong base (alkali) commonly known as caustic soda. Its molecular weight is calculated by adding the atomic masses of sodium (Na = 23), oxygen (O = 16), and hydrogen (H = 1).

Question (Click to Flip)

What is the molecular weight of NaOH?

Answer

The molecular weight of NaOH (sodium hydroxide) is 40 g/mol. Calculation: Na (23) + O (16) + H (1) = 40 g/mol.

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Key Facts

Molecular weight of NaOH = 40 g/mol

NaOH = Na (23) + O (16) + H (1) = 40

Common name: Caustic soda or Lye

Strong base: completely ionises in water

NaOH + HCl → NaCl + H₂O (neutralisation)

Used in soap making (saponification), paper industry, drain cleaners

Calculation of Molecular Weight of NaOH

Formula: NaOH = Na + O + H

Atomic masses:

  • Na (Sodium) = 23 u
  • O (Oxygen) = 16 u
  • H (Hydrogen) = 1 u

Calculation: Molecular weight = 23 + 16 + 1 = 40 g/mol

Answer: Molecular weight of NaOH = 40 g/mol

Properties and Uses of NaOH

Common name: Caustic soda, Lye Chemical name: Sodium hydroxide Formula: NaOH Molecular weight: 40 g/mol Physical state: White solid (pellets or flakes) Solubility: Highly soluble in water (exothermic dissolution) pH: ~14 (strongly alkaline in solution)

Chemical nature:

  • Strong base — completely ionises in water: NaOH → Na⁺ + OH⁻
  • Highly corrosive (hence 'caustic')

Industrial and common uses:

  • Soap and detergent manufacturing (saponification)
  • Paper and pulp industry
  • Textile processing (mercerizing cotton)
  • Drain cleaners (dissolves fats and proteins)
  • Food processing (making pretzels, olives, ramen noodles)
  • Chemical synthesis and water treatment

Important Reactions of NaOH

  1. Neutralisation (acid-base): NaOH + HCl → NaCl + H₂O

  2. With CO₂: 2NaOH + CO₂ → Na₂CO₃ + H₂O

  3. Saponification (soap making): Fat/oil + NaOH → Soap (sodium salt of fatty acid) + Glycerol

  4. With metals (amphoteric): 2NaOH + 2Al + 2H₂O → 2NaAlO₂ + 3H₂↑

  5. With non-metals: 2NaOH + Cl₂ → NaCl + NaOCl + H₂O (used in bleach production)

Questions and Answers

What is the molecular weight of NaOH?+

The molecular weight of NaOH (sodium hydroxide) is 40 g/mol. Calculation: Na (23) + O (16) + H (1) = 40 g/mol.

What is the common name of NaOH?+

NaOH is commonly known as caustic soda or lye. Its IUPAC name is sodium hydroxide. It is a strong base used in soap making, paper production, and as a drain cleaner.

Why is NaOH called caustic soda?+

NaOH is called caustic soda because it is highly corrosive ('caustic' means capable of burning or corroding). It can severely damage skin, eyes, and other materials. 'Soda' refers to its sodium content. It is also called lye.

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