Water (H₂O) sometimes likes to split into ions, H⁺ and OH⁻: H₂​O (l) ⇌ H⁺ (aq)+ OH⁻(aq)

🧪 Equilibrium and Water

• Equilibrium Constant (K): It’s like a scoreboard for the water splitting game, showing the concentration of each player - K =\(\frac {[H^+][OH^-]}{[H_2O]}\)

• Ionic Product of Water (Kw): Here’s where the action gets exciting! It’s the product of the concentrations of the ions when water is at equilibrium - Kw = [H⁺][OH⁻]

  • Room Temperature: Kw =1.00 ×10⁻¹⁴ (only for dilute solutions!)
  • Fun Fact: Only one in about 1,800,000,000 water molecules breaks into ions!

• Hotter Water = Higher Kw! More water molecules break into ions when it’s hot.
• In concentrated solutions (like battery acid), less water, so different Kw.

• When we dissolve things like Hydrogen Chloride (HCl) in water, more H⁺ ions join the party!
• More H⁺ ions make the solution acidic, which means less OH⁻ ions, as they don’t get along well. So, in acidic solutions, we always have more H⁺ ions than OH⁻ ions.
• Real World Example: It’s like adding lemon juice to water, making a sour lemonade; more H⁺ ions mean a more sour solution!

• Adding a base means more OH⁻ ions and fewer H⁺ ions.
• Real World Example: It’s like adding baking soda to water, creating a basic (alkaline) solution; more OH⁻ ions mean a more basic solution!

Let’s calculate the concentration of OH⁻ ions in a 0.100 mol dm⁻³ HCl solution: [OH⁻] = \(\frac {1.00 × 10^{-14}}{0.100} = 1.00 × 10^{-13}\) mol dm⁻³ - 🤓 Meaning more H⁺ ions than OH⁻ ions, confirming it’s acidic!