Moles of Compounds
- Chemical formula: subscripts indicate…
o the number of atoms of that element in 1 molecule
o the number of moles of that element in 1 mol of a compound.
e.g. In H2O…2 atoms H in 1 molecule of H2O or 2 moles of H in 1 mole of H2O
1 mol O in 1 mol H2O (No subscript implied “1”)
*These are conversion factors*
How many moles of H in 1 mol of CH4?
4 mol of H in 1 mol of CH4
Subscripts outside of ( ) distributes and multiplies everything.
How many moles of O in 1 mol of Ba(NO3)2?
2 x 3 = 6 mol O in 1 mol of Ba(NO3)2
Mol Ba?
1 mol Ba in 1 mol Ba(NO3)2
Conversions:
How many mol H are in 2.5 mol H2O?
2.50 𝑚𝑜𝑙 𝐻! 𝑂
2 𝑚𝑜𝑙 𝐻
? 𝑚𝑜𝑙 𝐻 =
×
= 5.0 𝑚𝑜𝑙 𝐻
1 𝑚𝑜𝑙 𝐻! 𝑂
How many moles of O are in 3.8 moles Ba(NO3)2?
3.8 𝑚𝑜𝑙 𝐵𝑎(𝑁𝑂! )!
6 𝑚𝑜𝑙 𝑂
? 𝑚𝑜𝑙 𝑂 =
×
= 23 𝑚𝑜𝑙 𝑂
1 𝑚𝑜𝑙 𝐵𝑎(𝑁𝑂! )!
Molar Mass of Compound
- Multiple the # of each element in compound (subscripts) by its MM (*PT*)
and add them together.
MM H2O: 2 mol H 1.008 g H
1 mol O
16.00 g
2.016 g H
16.00 g O
------------- x ------------- + --------------- x -------------- = ---------------- + -------------- =
1 mol H20 1 mol H
1 mol H20 1 mol O
1 mol H20 1 mol H20
18.02 g H2O/mol H2O
What is the molar mass of Ba(NO3)2?
Ba = 1 x 137.33 g/mol = 137.3 g/mol
N = 2 x 14.01 g/mol = 28.02 g/mol
O = 6 x 16.00 g/mol = 96.00 g/mol
+ -------------------------------------------------------Molar Mass of Ba(NO3)2 = 261.4 g/mol **Now you can use this
as a conversion factor!!