Sodium hydroxide is a common chemical compound that readily forms aqueous solutions. When mixed with water, it dissolves to create a strong base, meaning it has a high pH. This dissolved form is widely used in various industrial and household applications.
What “Aqueous” Means
In chemistry, “aqueous” describes a solution where water acts as the solvent. A solvent dissolves another substance, called the solute. When a solute dissolves in water, its particles disperse evenly, creating a homogeneous mixture. This means the mixture has a uniform composition throughout, without distinct layers or separated components. Water’s unique molecular structure makes it an excellent solvent for many substances. Many chemical reactions occur in aqueous environments because the dissolved state allows for easier interaction between reactant molecules. Understanding aqueous solutions is fundamental to comprehending how substances, including sodium hydroxide, behave when combined with water.
Why Sodium Hydroxide Dissolves So Readily
Sodium hydroxide (NaOH) dissolves readily in water due to its ionic nature. It is composed of positively charged sodium ions (Na+) and negatively charged hydroxide ions (OH-).
Water molecules, while electrically neutral overall, are polar. They have a slight positive charge on their hydrogen atoms and a slight negative charge on their oxygen atom. This polarity allows water to interact strongly with charged ions.
When solid sodium hydroxide is introduced into water, polar water molecules surround and attract the individual Na+ and OH- ions. The slightly negative oxygen ends of water molecules are drawn to the positive sodium ions, while the slightly positive hydrogen ends are attracted to the negative hydroxide ions. This process, known as hydration, pulls the ions away from the solid crystal lattice and into the solution. The strong attractive forces between water molecules and ions overcome the ionic bonds holding solid NaOH together, leading to its complete dissociation and high solubility.
Understanding Its Properties in Water
Once sodium hydroxide dissolves in water, it forms a highly alkaline solution. This is because the dissolution process releases a large concentration of hydroxide ions (OH-). The presence of these hydroxide ions is directly responsible for the solution’s high pH, typically ranging from 13 to 14 for concentrated solutions.
Aqueous sodium hydroxide is highly corrosive and can cause severe chemical burns upon contact with skin or eyes. This corrosive nature stems from its ability to react with and break down organic materials, including proteins and fats. It also reacts vigorously with acids in a neutralization reaction, producing water and a salt. These properties make aqueous sodium hydroxide a potent chemical that requires careful handling.
Common Applications and Safety
Aqueous sodium hydroxide is used in numerous industrial and household applications. It is a common ingredient in drain cleaners, dissolving grease and hair to clear blockages. The solution is also used in producing soap, paper, and textiles, and in various chemical manufacturing processes. Its strong basicity makes it valuable for adjusting pH levels in water treatment and neutralizing acidic waste streams.
Handling aqueous sodium hydroxide requires strict safety precautions due to its corrosive nature.
- Always wear appropriate personal protective equipment, including chemical-resistant gloves, eye protection (safety goggles or a face shield), and protective clothing.
- Ensure adequate ventilation to avoid inhaling mists.
- In case of spills, neutralize the solution with a weak acid, such as vinegar, before cleaning.
- Always have access to an eyewash station and safety shower.