What happens when dilute hydrochloric acid is added to iron fillings? 

Hydrogen gas and iron chloride are produced.

The correct answer is option 1. Hydrogen gas and iron chloride are produced.

When dilute hydrochloric acid \((HCl)\) is added to iron fillings \((Fe)\), a chemical reaction occurs. This reaction is a classic example of a single displacement reaction, where one element displaces another in a compound. The reaction can be represented by the following equation:

\[ \text{Fe (s)} + 2HCl (aq) \rightarrow FeCl_2 (aq) + H_2 (g) \]

In this reaction:

Iron \((Fe)\) reacts with hydrochloric acid \((HCl)\).

The iron displaces the hydrogen in the hydrochloric acid to form iron chloride \((FeCl_2)\) and hydrogen gas \((H_2)\).

Iron chloride is a soluble compound that remains in the solution.

Hydrogen gas is released as a product and can be observed as bubbles.

So, the overall result of adding dilute hydrochloric acid to iron fillings is the production of hydrogen gas and iron chloride.