Water and Solutions PT2

Solubility of Gases in Liquids

• Gases dissolve more effectively in liquids at lower temperatures; for example, oxygen is more soluble in cold water than in warm.

• Hot water discharged into lakes raises the temperature and reduces dissolved oxygen levels, harming aquatic life.

• Pressure affects gas solubility: higher partial pressure increases gas dissolution in liquids due to greater particle collisions.

• Example: In carbonated drinks, carbon dioxide gas is dissolved. When the container is opened, pressure drops, decreasing solubility, leading to gas escaping from the solution.

Solubility of Gases in Liquids

Key Concepts:

• Temperature Impact: Gases, like oxygen, dissolve better in cold liquids than warm ones.

• Environmental Consequences: Hot water increases temperatures in lakes, decreasing dissolved oxygen and harming aquatic life.

• Pressure Effect: Higher pressure boosts gas solubility due to more frequent particle collisions.

Examples:

• Carbonated Drinks: Carbon dioxide dissolves under pressure; upon opening, pressure drops, and gas escapes.

Salinity in Water Bodies:

• The Atlantic Ocean is generally saltier than the Pacific.

• The Black Sea has lower salinity due to freshwater inflows.

• Evaporation increases salinity in areas like the Mediterranean and Red Sea.

• The Dead Sea is one of the saltiest bodies of water.

Molarity Defined:

• Concentration of solute in a solution (moles of solute per liter of solution).

• Example: A 2 M solution has 2 moles of solute per liter.

Example Calculation: Molarity of NaOH

1. Convert grams to moles using molar mass.

2. Convert milliliters to liters for the volumetric calculation.

3. Use the formula: Molarity = moles of solute / liters of solution.

4. Keep significant figures during the calculation.