Question

How do you change 8.5 g of `SiH_4` to moles?

Answer 1

8.5g `SiH_4` `*` `(1 mol)/(32.122g SiH_4)` = 0.2646 moles `SiH_4`

Explanation:

When converting to moles, you always start with the mass in grams of your substance. In this case 8.5g `SiH_4`.

In order to convert to moles you will need to find the molecular mass of the molecule. You can do this using the molecular formula `SiH_4`.

Use the values on a periodic table titled "relative atomic mass" or "molecular mass" for each element. This is what a single mole of this atom would weigh.

Silicon (Si) weighs 28.09 grams.
Hydrogen (H) weighs 1.008 grams.

You have 1 Si atom and 4 H atoms, so add together the mass of 1 Si and 4 H.

Si + 4(H) = molar mass of `SiH_4`
`28.09g+(4*1.008)g = 32.122g`

Now you just divide the grams of `SiH_4` that you have by the molar mass of `SiH_4` and you will be able to find the number of moles.

This equation is how this process is commonly written. It begins with the grams of `SiH_4` and multiplies by the grams/mole of `SiH_4` atomically (molar mass). The grams will cancel leaving you with only moles.
8.5g `SiH_4` `*` `(1 mol)/(32.122g SiH_4)` = 0.2646 moles `SiH_4`