How to know if a metal reacted with an acid

Hydrogen gas will be given off

Explanation:

Whenever a metal reacts with an acid, a salt of the metal is formed and hydrogen gas is given off.

For instance: The reaction of Zinc metal on Hydrochloric acid.

Zn(s) + 2HCl(aq) ---> ZnCl2(aq) + H2(g)

From the equation provided, hydrogen gas is given off as a by-product

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !