Given the balanced reaction: Zn + 2HCl H2 + ZnCl2 How many grams of zinc are needed to produce 5 grams of H2?

Explanation:

Hello there!

In this case, according the given balanced chemical reaction:

It is possible to evidence the 1:1 mole ratio of hydrogen (molar mass = 2.02 g/mol) to zinc (atomic mass = 65.41 g/mol) which is used to calculate the grams of the latter needed for the production of 5 grams of the former via stoichiometry:

Best regards!

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 !