A student adds \[AgN{O_3}\] to HCl. Which of the following should the student easily observe?
I. A precipitate is formed
II. The solution turns yellow
Ill. Bubbles are produced as a gas is evolved
A. I only
B. II only
C. III only
D. I and II only

Hint: According to the question, we will make silver nitrate react with hydrochloric acid and observe the reaction taking place. A milky, white and clouded solution is formed which settle down at bottom as a distinctive solid. Filtering and weighing this solid will tell us the amount of silver nitrate used.

Complete answer:
As per the question, when the student will add \[AgN{O_3}\] to HCl, the following reaction will take place,
 \[AgN{O_3}(aq) + HCl(aq) \to AgCl(s) \downarrow + HN{O_3}(aq)\]
- The reaction taking place is an example of an acid-base reaction also called a neutralization reaction.
- The addition of colourless aqueous silver nitrate to hydrochloric acid produces a white curd-like insoluble precipitate of silver chloride. This reaction is also a common test to check the presence of chloride ions.
- On the other hand, the solution turns yellow, when a colourless solution of lead (II) nitrate is added to a colourless solution of potassium iodide, a yellow solid which is a precipitate. And bubbles are produced as a result of zinc reacting with hydrochloric acid, the reaction bubbles vigorously as hydrogen gas is produced.

Hence, option A is correct that a precipitate is formed.

Note: The precipitate obtained on the reaction of \[AgN{O_3}\] and HCl is a curd-like white precipitate of AgCl, which is further tested in labs as the obtained ppt. is soluble in ammonium hydroxide solution and insoluble in dilute nitric acid.