Which of the following is a base?

Which of the following is a base?

• A. CH3COOH
• B. CH3OH
• C. NaCl
• D. KOH

Answer: (D)

A base is a substance that increases the hydroxide ion concentration in water (Arrhenius) or, in Bronsted–Lowry terms, a substance that accepts a proton. Potassium hydroxide does this clearly: when it dissolves, it dissociates into K+ and OH-. The hydroxide ions raise the pH and can accept protons from acids, making the solution basic. The other options don’t fit as bases in typical aqueous chemistry: acetic acid donates a proton, so it’s an acid; methanol is an alcohol and is not considered a base in this context; sodium chloride is a neutral salt that doesn’t change the OH− concentration significantly.

A base is a substance that increases the hydroxide ion concentration in water (Arrhenius) or, in Bronsted–Lowry terms, a substance that accepts a proton. Potassium hydroxide does this clearly: when it dissolves, it dissociates into K+ and OH-. The hydroxide ions raise the pH and can accept protons from acids, making the solution basic. The other options don’t fit as bases in typical aqueous chemistry: acetic acid donates a proton, so it’s an acid; methanol is an alcohol and is not considered a base in this context; sodium chloride is a neutral salt that doesn’t change the OH− concentration significantly.