E

Effective Molality

m_eff = i × m (van't Hoff factor)
Quick Reference
Formula / Notationm_eff = i × m (van't Hoff factor)
Also Known Asvan't Hoff molality; corrected molality; i × m; particle-corrected molality

What is Effective Molality?

Effective molality accounts for the actual number of particles produced when a solute dissolves, by multiplying the nominal molality (m) by the van't Hoff factor (i). For electrolytes, i > 1 because dissociation produces more particles than formula units. It is used to calculate accurate values of colligative properties such as boiling point elevation and freezing point depression.

Formula & Notation

m_eff = i × m (van't Hoff factor)

Other Names / Synonyms: van't Hoff molality; corrected molality; i × m; particle-corrected molality

Properties & Characteristics

Effective molality = i × m; van't Hoff factor i: number of particles per formula unit; NaCl: i ≈ 2; CaCl₂: i ≈ 3; non-electrolytes: i = 1; i approaches ideal value at infinite dilution; activity corrections needed at high concentrations

Uses & Applications

Accurate calculation of colligative properties for electrolyte solutions; osmotic pressure calculations in biological systems; cryoscopy and ebullioscopy with salt solutions; pharmaceutical formulation

Safety Information

No direct hazard — a solution chemistry concept.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Effective Molality
Formula m_eff = i × m (van't Hoff factor)
Synonyms van't Hoff molality; corrected molality; i × m; particle-corrected molality

Frequently Asked Questions

Effective molality accounts for the actual number of particles produced when a solute dissolves, by multiplying the nominal molality (m) by the van't Hoff factor (i). For electrolytes, i > 1 because dissociation produces more particles than formula units. It is used to calculate accurate values of colligative properties such as boiling point elevation and freezing point depression.

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