Download Gram Formula Mass – Complex (1 of 4) GFM: complex A subscript is

GFMPartTwo1.swf
Home: Stoichiometry: Gram Formula Mass – Complex (1 of 4)
GFM: complex
A subscript is the small number following an element symbol or parenthesizes.
The subscript tells you how many of each element there are in a compound.
If the subscript comes after parenthesizes, you multiply it by all the elements within the parenthesizes.
Image with Ca(NO3)2 and an arrow point to the subscript.
Arrow to 3 “there are three O atoms” Arrow to 2 “there are two N atoms and six O atoms”
You can think of a compound like Ca(NO3)2 having one Ca atoms with two NO3 ions attached.
Image of Ca with two NO3’s attached.
CTAT1
How many Os are there is in:
Ca(NO3)2
Ca(NO2)2
NaOH
Ca(OH)2
How many H’s are there in:
Na(OH)
Mg(OH)2
Al(OH)3
CTAT2
Finding the GFM -Text - To find the GFM:
1. Determine how many of each element is in the compound.
2. Multiply the number of each element by its GAM.
3. Add the numbers together to find the GFM for the compound.
Here I can do a walk-through of a sample compound - Ca(NO3)2.
1. Find the number of each element.
Ca = [1]
N= [2]
O = [6]
2. Multiply the number of each element by its GAM.
Ca = 1 x [40.08] g/mol = [40.08] g/mol
N = 2 x [14.01] g/mol = [28.02] g/mol
O = 6 x [15.99] g/mol = [95.94] g/mol
3. Add the numbers together to get the GFM for Ca(NO3)2 which is [164.04 g/mol].
CTAT 2
Same thing but for Al(OH3).
CTAT3
Order the following steps in calculating the GFM for a compound with parentheses.
Find the GFM for Ca3(PO4)2.
Find the GFM for Al2(SO4)3
Quiz
Which is the correct representation of Ca(OH)2?
How many oxygen atoms are in Mg(NO3)2?
How many oxygen atoms are in Mg(NO2)2
Four GFM calculations involving parenthesis.
Find the GFM for
Ca(ClO4)2 -- 238.98
Mg(C2H3O)2 110.41
Al(NO2)3
165.01
The subscript for the oxygen in CaSO4 is four. What is the subscript for element sulfur?
multiple choice here.
Maybe
Order the following steps in calculating the GFM for a compound with parentheses.
Step 1 -- Find the number of each element. Multiply each number inside parentheses by the subscript
outside of the parentheses.
This is tougher because there are more ways to interpret the problem. It feels like all I need to do in
this section is show them how to calculate the GFM when there are parenthesizes. They know what the
subscript is already form the GFM simple. So here
Add another option section – step-by-step examples.