Final answer:
In general, when an acid and a base are mixed, 4) water and salt are formed.
Step-by-step explanation:
When an acid and a base are mixed together, they undergo a neutralization reaction. This type of chemical reaction typically results in the formation of water and a salt, which is an ionic compound. A commonly cited example of this is the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH), resulting in sodium chloride (NaCl) and water (H₂O):
HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)
This demonstrates the general pattern for an acid-base reaction, which can be simplified to:
acid + base → water + salt
The salt produced can have varying properties in solution, potentially resulting in a neutral, basic, or acidic solution depending on the specific ions present.
Hence, the correct answer is Option 4.