Mixture Chemistry Example 4

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Example 4

hard
Seawater contains dissolved salts (3.5%\sim 3.5\%), dissolved gases, and suspended particles. Classify seawater as a type of mixture and outline a procedure using at least three separation techniques to isolate the dissolved salt, fresh water, and suspended particles.

Solution

  1. 1
    Seawater is primarily a homogeneous mixture (solution) with some heterogeneous components (suspended particles).
  2. 2
    Step 1 — Filtration: removes suspended particles (sand, plankton) based on particle size. Step 2 — Distillation: heat the filtered water to boil off and collect pure water as the distillate. Step 3 — Evaporation: allow the remaining concentrated salt solution to evaporate completely, leaving behind solid salt crystals.
  3. 3
    Each technique exploits different physical properties: particle size (filtration), boiling point (distillation), and state change (evaporation).

Answer

Filter (particles) → distill (fresh water) → evaporate (salt)\text{Filter (particles) → distill (fresh water) → evaporate (salt)}
Desalination of seawater is a real-world application of mixture separation techniques. Modern desalination plants use reverse osmosis (membrane separation) as a more energy-efficient alternative to distillation.

About Mixture

A physical combination of two or more substances that are not chemically bonded, retain their individual properties, exist in variable proportions, and can be separated.

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