In the reaction, 2h2 o2 --> 2h2o, how many hydrogen molecules are needed to produce two water molecules? a. 1b. 2c. 3d. 4

b. 2

There are necessary 2 hydrogen molecules to produce 2 water molecules.

Explanation:

The balanced equation is already given:

So, 2 molecules of diatomic hydrogen react with 1 molecule of diatomic oxygen to obtain 2 water molecules.

As you can see in the attached image, the 2 molecules of diatomic hydrogen have 2 hydrogen atoms each (i.e. 4 hydrogen atoms), the molecule of diatomic oxygen has 2 oxygen atoms and the 2 water molecules have 2 hydrogen atoms and 1 oxygen atom each (i.e. 4 hydrogen atoms and 2 oxygen atoms)

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 !