Question

question 1
when a weak acid is added to water, it...
...does not dissociate.
...dissociates partially.
...dissociates completely.
...precipitates.
question 2
what does partial dissociation of a weak acid in water produce?
only hydronium ions.
only anions related to the acid.
hydronium ions and related anions.
a complete neutralization reaction.

Explanation:

Weak acids, by definition, partially dissociate in water. Strong acids dissociate completely. Precipitation is a different chemical process (formation of a solid from a solution). A complete neutralization reaction is a different type of reaction (acid - base reaction resulting in salt and water). Since the question is about the dissociation of a weak acid in water, the key concept is partial dissociation.

Answer:

For Question 1: "dissociates partially"
For Question 2: "Hydronium ions and related anions"