Option 1: Hg (Mercury)
Mercury is a metal that is not very reactive. It does not react with dilute HCl to produce hydrogen gas (H2). This is because mercury is low on the reactivity series of metals.
Option 2: Al (Aluminum)
Aluminum is a metal that is reactive, but it does react with dilute HCl to produce hydrogen gas (H2). Aluminum displaces hydrogen from the acid, forming aluminum chloride and hydrogen gas.
Option 3: Mg (Magnesium)
Magnesium is a metal that is highly reactive. It reacts vigorously with dilute HCl to release hydrogen gas (H2). Magnesium displaces hydrogen from the acid, forming magnesium chloride and hydrogen gas.
Option 4: Fe (Iron)
Iron is a reactive metal and does react with dilute HCl to produce hydrogen gas (H2). Iron displaces hydrogen from the acid, forming iron chloride and hydrogen gas.
In summary, options 2, 3, and 4 will react with dilute HCl to produce hydrogen gas, whereas option 1 (Mercury) will not react and is the correct answer.