The concentration of hydroxide (OH⁻) ions in a certain household ammonia cleaning solution is 0.0025 M.
Household ammonia, commonly used as a cleaning agent, is an aqueous solution of ammonia (NH₃). When ammonia dissolves in water, it undergoes a reversible reaction with water to form ammonium ions (NH₄⁺) and hydroxide ions (OH⁻), making the solution alkaline. This alkalinity is what gives household ammonia its powerful cleaning properties, particularly for cutting through grease and grime.
Understanding Household Ammonia and Hydroxide Ions
Household ammonia is essentially a diluted solution of ammonia gas dissolved in water. It is a weak base, meaning it does not fully dissociate in water, but it produces enough hydroxide ions to make the solution significantly alkaline. The presence and concentration of these hydroxide ions are crucial for its function.
Key characteristics:
- Alkaline Nature: Due to the production of OH⁻ ions, household ammonia solutions have a high pH, typically above 11.
- Cleaning Power: The hydroxide ions react with fats, oils, and grease, breaking them down into water-soluble compounds that can be easily rinsed away.
- Volatile: Ammonia gas can evaporate from the solution, which is why it has a characteristic pungent odor and why good ventilation is recommended during use.
The Exact Concentration of Hydroxide Ions
For a specific household ammonia cleaning solution, the concentration of hydroxide ions has been determined to be very precise.
| Component | Concentration (Molarity) |
|---|---|
| Hydroxide (OH⁻) | 0.0025 M |
This value, 0.0025 M, indicates the molar concentration of OH⁻ ions, meaning there are 0.0025 moles of hydroxide ions per liter of the solution.
Importance of OH⁻ Concentration
The concentration of hydroxide ions is a direct measure of a solution's alkalinity or basicity. In the context of household ammonia:
- Cleaning Effectiveness: A higher concentration of OH⁻ ions generally indicates a stronger base and thus more effective cleaning power for certain types of stains.
- pH Determination: The hydroxide ion concentration is inversely related to the hydrogen ion (H⁺) concentration and is fundamental to calculating the pH of the solution. The relationship is governed by the ion product of water (Kw), where Kw = [H⁺][OH⁻] = 1.0 x 10⁻¹⁴ at 25°C. Knowing [OH⁻] allows for the calculation of pOH (pOH = -log[OH⁻]) and subsequently pH (pH = 14 - pOH).
Understanding the precise concentration of hydroxide ions helps in assessing the chemical properties and cleaning efficacy of household ammonia products.
