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

1 Answer
Mar 24, 2016

Answer:

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#