# Acid-base theory problems and solutions

1. What is an acid according to Arrhenius theory? Solution: According to Arrhenius theory, an acid is a substance that when dissolved in water, increases the concentration of H⁺ ions.

2. What is a base according to Arrhenius theory? Solution: According to Arrhenius theory, a base is a substance that when dissolved in water, increases the concentration of OH⁻ ions.
3. How does the Bronsted-Lowry theory define acids and bases? Solution: The Bronsted-Lowry theory defines an acid as a proton (H⁺ ion) donor and a base as a proton (H⁺ ion) acceptor.
4. How does the Lewis theory define acids and bases? Solution: According to Lewis theory, an acid is an electron pair acceptor and a base is an electron pair donor.
5. What is a conjugate acid-base pair? Solution: A conjugate acid-base pair consists of two substances related to each other by the donating and accepting of a single proton.
6. What is the pH scale? Solution: The pH scale is a logarithmic scale that measures the acidity or basicity of a solution. It ranges from 0 (very acidic) to 14 (very basic), with 7 being neutral.
7. How is pH calculated? Solution: pH is calculated as the negative logarithm (base 10) of the activity of the hydrogen ion in a solution.
8. What is a strong acid? Solution: A strong acid is one that completely ionizes (dissociates) in a solution. Examples include hydrochloric acid (HCl) and sulfuric acid (H₂SO₄).
9. What is a strong base? Solution: A strong base is one that completely dissociates in water into the cation and OH⁻. Examples include sodium hydroxide (NaOH) and potassium hydroxide (KOH).
10. What is a weak acid? Solution: A weak acid is one that only partially ionizes in a solution. An example is acetic acid (CH₃COOH).
11. What is a weak base? Solution: A weak base is one that does not completely ionize in a solution. An example is ammonia (NH₃).
12. What does it mean for a solution to be neutral? Solution: A solution is neutral if its pH is 7. This means the concentration of H⁺ ions equals the concentration of OH⁻ ions.
13. What are amphoteric substances? Solution: Amphoteric substances can act as both acids and bases. An example is water (H₂O).
14. What is the pOH of a solution? Solution: pOH is the negative logarithm (base 10) of the hydroxide ion concentration.
15. What is the relationship between pH and pOH at 25 degrees Celsius? Solution: At 25°C, pH + pOH = 14.
16. What is the ion-product of water? Solution: The ion-product of water, Kw, is the product of the concentrations of H⁺ and OH⁻ ions at 25°C. Its value is 1.0 x 10⁻¹⁴.
17. What is the process of neutralization? Solution: Neutralization is a chemical reaction between an acid and a base that results in the formation of water and a salt.
18. What is titration? Solution: Titration is a technique used to determine the concentration of an unknown solution (acid or base) by adding a solution of known concentration until the reaction between them is just complete.
19. What is an indicator? Solution: An indicator is a substance that changes color at (or near) the equivalence point of a chemical reaction, often used in titration.
20. What is the role of a buffer solution? Solution: A buffer solution is a solution that can resist changes in pH when small amounts of an acid or a base are added. It is usually made from a weak acid and its conjugate base, or a weak base and its conjugate acid.