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

Mar 24, 2016

8.5g $S i {H}_{4}$$\cdot$ $\frac{1 m o l}{32.122 g S i {H}_{4}}$ = 0.2646 moles $S i {H}_{4}$

#### Explanation:

When converting to moles, you always start with the mass in grams of your substance. In this case 8.5g $S i {H}_{4}$.

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 $S i {H}_{4}$.

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 $S i {H}_{4}$
$28.09 g + \left(4 \cdot 1.008\right) g = 32.122 g$

Now you just divide the grams of $S i {H}_{4}$ that you have by the molar mass of $S i {H}_{4}$ 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 $S i {H}_{4}$ and multiplies by the grams/mole of $S i {H}_{4}$ atomically (molar mass). The grams will cancel leaving you with only moles.
8.5g $S i {H}_{4}$$\cdot$ $\frac{1 m o l}{32.122 g S i {H}_{4}}$ = 0.2646 moles $S i {H}_{4}$