How many moles are in 15.5 g #SiO_2#?

1 Answer
Feb 20, 2016

Answer:

About a 1/4 of a mole.

Explanation:

Silicon dioxide has a molar mass of #60.08# #g# #mol^-1#. What does this mean? It means that Avogadro's number of #SiO_2# units has a mass of #60.08# #g#.

So to find the molar quantity of silicon dioxide, all I have to do is divide the mass by the molar mass:

#"Moles of silicon dioxide " = "Mass"/"Molar Mass"#

#=# #(15.5*cancelg)/(60.08*cancelg*mol^-1)# #=# #??# #mol#

By doing the equation with units included it helps to prevent me from making mistakes. Should I divide or should I multiply? The fact that the calculation gave me an answer in moles persuades me that I did the right thing. It's all too easy to make a mistake.

What is silicon dioxide? How do you calculate its molar mass?