MYP Chemistry Uses of Salts Notes

How Do Properties of Salts Make Them Useful or Hazardous?

Salts are not all the same. Their properties determine whether they are helpful, harmful, or both:

1. Solubility – how well they dissolve in water.
2. Hygroscopicity – ability to absorb water from the air.
3. Toxicity – how harmful they are to living organisms.

Solubility

Highly Soluble Salts

1. Example: Sodium chloride, NaCl
   1. Dissolves easily in water.
   2. Forms ions that move freely → important for electrolyte solutions and de-icing roads.
2. Advantages:
   1. Easy to dissolve and spread.
   2. Cheap and widely available.
3. Risks:
   1. Runoff can increase soil and water salinity, harming plants and aquatic life.
   2. Corrodes metal structures (cars, bridges).

Low-Solubility Salts

1. Example: Barium sulfate, BaSO₄
   1. Very poorly soluble in water.
   2. Because it does not dissolve, it is not absorbed by the body.
2. Advantages:
   1. Good contrast agent for imaging.
   2. Passes through the body without entering the bloodstream.
3. Risks:
   1. If a soluble barium salt were used by mistake, it would be highly toxic.
   2. Must be used only under medical supervision.

Ability to Absorb Water (Hygroscopicity)

Some salts can absorb water from the air; some even form hydrated crystals or turn into a solution.

Desiccants (Drying Agents)

1. Examples: Calcium chloride (CaCl₂), magnesium sulfate (MgSO₄)
   1. Used to keep things dry by absorbing moisture from their surroundings.
   2. Often found in small sachets in electronics, shoe boxes, medicine bottles.
2. Advantages:
   1. Prevents corrosion, mould and spoilage.
   2. Useful in packaging, laboratories, and industry.
3. Risks:
   1. Can cause corrosion if they release absorbed water in the wrong place.
   2. Some can cause skin and eye irritation – handle with care and avoid ingestion.

Toxicity

Not all salts are safe. Some are essential nutrients; others are highly toxic.

Beneficial Salts

Examples:

1. Potassium chloride (KCl) – used in fertilisers to provide potassium, an essential nutrient for plants.
2. Sodium chloride (NaCl) – needed in small amounts in our diet to regulate fluid balance and nerve function.

Toxic or Hazardous Salts