Question

what does the ph scale measure?
concentration of salts
temperature of a solution
concentration of hydrogen ions
amount of oxygen in water

what is a buffer?
a solution that resists changes in ph
a substance that neutralizes acids and bases
a solution that only changes color in acidic conditions
a chemical that changes color at different ph levels

Explanation:

• For the first question: The pH scale is a measure of the concentration of hydrogen ions ($H^+$) in a solution. The formula for pH is $pH = -\log[H^+]$, where $[H^+]$ is the molar concentration of hydrogen ions.
• For the second question: A buffer is a solution that resists changes in pH when small amounts of acid or base are added. It typically consists of a weak acid and its conjugate base or a weak base and its conjugate acid.

Answer:

• First question: Concentration of hydrogen ions
• Second question: A solution that resists changes in pH