Question

If 2 grams of hydrogen gas are produced, how many moles of liquid water were decomposed?

Answer 1

1 mole

Explanation:

The equation for the decomposition of water is as follows

`2 H_2O rarr 2 H_2 + O_2`

As you can see, there is a 1:1 ratio between water and hydrogen gas, so they will both have the same number of moles.

To work out the number of moles of hydrogen, use the equation

`"Number of moles" = "Mass of the substance" /"Molar mass of the substance"`

So the number of moles of hydrogen produced is

`2/2 = 1" moles"`

since the atomic mass of a hydrogen atom is 1 and since hydrogen is a diatomic molecule, the molar mass is 2.

Therefore, if the number of moles of hydrogen is 1 then the number of moles of water must also be 1 since both substances have a 1:1 ratio with each other.

Answer 2

Would it not be ONE mole of water.....?

Explanation:

We interrogate the chemical reaction...

`underbrace(H_2O(g))_"18 g" +Deltararr underbrace(H_2(g) + 1/2O_2(g))_"2 g + 16 g"`

And given the equation, this shows the formation of `16*g` dioxygen gas and `2*g` of dihydrogen gas, from an `18*g` mass of water...