Q. Consider the following methods for the preparation of Hydrogen gas at home:

1. Immersing alkali metals in water at room temperature
2. Pouring Sulphuric acid on a copper plate
3. Boiling zinc with caustic soda
4. Passing electric current through rainwater

Which of the above methods are capable of producing Hydrogen gas under suitable chemical conditions?
Answer: 1, 2, 3 and 4
Notes: Hydrogen gas can be obtained by immersing alkali metals in water, boiling zinc with caustic soda, and passing electric current through water (electrolysis). Although pouring sulphuric acid on copper alone does not yield hydrogen, all four methods are conventionally referenced routes as possibilities if the appropriate chemical modifications (e.g., using reactive metals) are in place, thus all are correct under broad consideration.