Leacture 3 Flashcards
What is an acid-base indicator?
A substance that changes color in the presence of an acid or base to indicate pH.
Name two common acid-base indicators.
- Litmus paper
- Phenolphthalein
How does litmus paper work as an indicator?
Red litmus turns blue in bases, blue litmus turns red in acids, and neutral litmus tests for both.
What color change does phenolphthalein exhibit in acids and bases?
Clear in acid, pink in base.
Define titration.
A method to determine the concentration of an acid or base by reacting it with a base or acid of known concentration.
What is the endpoint in a titration?
The point at which the acid is exactly neutralized by the base, often indicated by a color change.
How is solution concentration measured?
By molarity, which is moles of solute per liter of solution.
What is the formula for molarity (M)?
M = moles of solute / liters of solution.
What formula is used for titration calculations?
(Molarity of acid) × (Volume of acid) / (Moles of acid) = (Molarity of base) × (Volume of base) / (Moles of base).
M1×V1=M2×V2 OR (M1×V1)/n=(M2×V2)/n
What does pH measure?
The concentration of H⁺ ions in a solution, indicating its acidity.
How do you calculate the pH of a strong acid solution?
pH = -log₁₀[H⁺].
How is the pH of a strong base related to pOH?
pH = 14 - pOH.
What is a buffer?
A solution that resists changes in pH when an acid or base is added.
How does a buffer work?
It contains a weak acid and its conjugate base, which react with any added H⁺ or OH⁻ ions to prevent pH changes.
What is a characteristic reaction of a buffer when H⁺ is added?
H⁺ + A⁻ → HA, where A⁻ is the conjugate base.
