Based on the arrhenius theory, when potassium
hydroxide dissolves in water, the only negative
ion in the aqueous solution is
(1) o2 (aq) (3) h (aq)
(2) oh2 (aq) (4) oh (aq)

Answer : The correct option is, (4) .

Explanation :

According to the Arrhenius theory, an acid is a substance that ionizes in water to gives ions (hydronium ions or hydrogen ions) and a base is a substance which ionizes in water to gives ions (hydroxide ions).

As we know that when the potassium hydroxide (KOH) dissolves in water or ionizes in water to gives ions (hydroxide ions) and ions (potassium ion). That means ion is a negative ion in aqueous solution and ions is a positive ion in aqueous solution.

Hence, the correct option is, (4) .

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)