Bases

Definition

Bases are a class of chemical compounds that are characterized by their ability to accept protons (H+ ions) and produce hydroxide ions (OH-) when dissolved in water. They are the counterparts to acids in the Brønsted-Lowry theory of acid-base reactions and play a crucial role in the structure and general properties of nonmetals.

5 Must Know Facts For Your Next Test

1. Bases are classified as strong or weak depending on the extent to which they dissociate in water to produce hydroxide ions.
2. Strong bases, such as sodium hydroxide (NaOH) and potassium hydroxide (KOH), completely dissociate in water, producing a high concentration of hydroxide ions.
3. Weak bases, such as ammonia (NH3) and baking soda (NaHCO3), only partially dissociate in water, producing a lower concentration of hydroxide ions.
4. The strength of a base is determined by its ability to accept protons and its ability to produce hydroxide ions in aqueous solutions.
5. Bases play a crucial role in maintaining the pH balance of the body, neutralizing excess acids, and facilitating various chemical reactions in living organisms.

Review Questions

• Explain the relationship between bases and the Brønsted-Lowry theory of acid-base reactions.
  • According to the Brønsted-Lowry theory, bases are defined as proton acceptors. When a base is dissolved in water, it accepts protons (H+ ions) from water molecules, producing hydroxide ions (OH-). This process is the opposite of the reaction that occurs with acids, which are proton donors. The ability of bases to accept protons and produce hydroxide ions is a key characteristic that distinguishes them from acids in the Brønsted-Lowry theory of acid-base reactions.
• Describe the differences between strong and weak bases and how they affect the pH of aqueous solutions.
  • The strength of a base is determined by its ability to dissociate in water and produce hydroxide ions (OH-). Strong bases, such as sodium hydroxide (NaOH) and potassium hydroxide (KOH), completely dissociate in water, resulting in a high concentration of hydroxide ions and a high pH (greater than 7) in the aqueous solution. Weak bases, such as ammonia (NH3) and baking soda (NaHCO3), only partially dissociate in water, producing a lower concentration of hydroxide ions and a lower pH (still greater than 7) compared to strong bases. The difference in the degree of dissociation and hydroxide ion concentration is what distinguishes strong and weak bases and their effects on the pH of aqueous solutions.
• Analyze the role of bases in maintaining the pH balance of the body and facilitating chemical reactions in living organisms.
  • Bases play a crucial role in maintaining the pH balance of the body by neutralizing excess acids. The body's pH must be tightly regulated within a narrow range (typically around 7.4) to ensure proper physiological function. Bases, such as bicarbonate ions (HCO3-), act as buffers in the body, helping to maintain this optimal pH level. Additionally, bases facilitate various chemical reactions in living organisms by providing the necessary hydroxide ions (OH-) as reactants or catalysts. For example, the digestive system uses bases like sodium bicarbonate (NaHCO3) to neutralize the acidic environment of the stomach, enabling the proper breakdown and absorption of nutrients. The body's ability to maintain pH balance and support essential chemical reactions is largely dependent on the presence and function of bases.

Related terms

Brønsted-Lowry Theory: A theory of acid-base reactions that defines acids as proton donors and bases as proton acceptors.

pH Scale:

A scale that measures the acidity or basicity of a solution, with values ranging from 0 to 14, where 7 is neutral, values less than 7 are acidic, and values greater than 7 are basic.

Hydroxide Ion (OH-): A negatively charged ion composed of one oxygen atom and one hydrogen atom, which is produced when a base is dissolved in water.