Question

How many moles of hydrogen are there in `25.3` `g` of methane, `CH_4`?

Answer 1

The answer is that there are `6.32` mol of hydrogen in `25.3` `g` of `CH_4`.

Explanation:

First step is to find the molar mass of methane:

Carbon is 12, hydrogen is 1, so `CH_4` is `12+4xx1=16`

Find the number of moles of `CH_4` in `25.3` `g`:

`n=m/M=25.3/16=1.58` mole

In each mole of `CH_4` there are 4 moles of hydrogen, so our answer is `4xx1.58=6.32` mol

Answer 2

There are 6.31 moles of hydrogen in 25.3 g of methane

Explanation:

Dividing 25.3 g of methane by its molar mass of 16.04 g gives you how many moles of methane are in 25.3 g of methane, and multiplying that number by the number of hydrogens (in this case, 4) gives you about 6.309 moles of hydrogen in 25.3 g of methane.

Answer 3

`3.16 " moles " H_2`

Explanation:

First, clarify whether you mean moles of `H_2` (the molecule) or moles of `H` (the atom). The second will be twice as much as the first.

For this example I will calculate the moles of the molecule, `H_2` as if it were the product of a reaction. Every mole of methane contains 2 moles of `H_2` (`4H`). So we just need to calculate the moles of methane from the mass and multiply by two.

`25.3g xx (1"mole")/(16g CH_4) = 1.581 " moles " CH_4`

`1.581 xx 2 = 3.16 " moles " H_2`