2BaSO4 and 3Ba(OH)2 both have a similar white powder appearance, and have many of the same uses. What is the total number of oxygen atoms for both compounds?
As far as formulas go, this is as hard as it gets. There are some formulas that have parentheses around some of the elements. In high school chemistry, you will learn all about what these parenthesis mean, and in college, you have to memorize them. They do have a really cool name for the part of the formulas that is in parenthesis-polyatomic (many atoms) ions (charged particles)-polyatomic ions.
The procedure to determine the atoms of each element is a little different when you have a polyatomic ion.
You need to look at the parenthesis first, just you do in Math.
In the example Ba3(PO4)2, right outside the parentheses is a subscript of 2. That means you have 2 (PO4) groups. You multiply everything in the parenthesis by 2. So far, this is what you have figured out about the number of atoms of each element: Ba-? P-2 O-8
Ba stands alone by itself, so the 2 outside of the parenthesis does NOT impact the number of atoms of Ba.
Ba-3 P-2 O-8
Number of total atoms 13
Number of molecules 1
Watch the video tutorial below for this formula
Determine the following in the formula: (NH4)2CO2
# of elements ______
Number of atoms of each element ____
Number of total atoms ______
Number of molecules ______
The answer and a video tutorial is below.
(NH4)2CO2
# of elements __4____
Number of atoms of each element
N-2 H-8 C-1 O-2
Number of total atoms __13____
Number of molecules _1_____
Last but not least, if you have a coefficient in front of the formula that has a polyatomic ion, here is how you determine the number of atoms of each element:
Pretend like the coefficient is not there, and find the number of atoms in one molecule.
Once you have the number of atoms of one molecule, multiply each atom count by the coefficient. This will give you the number of atoms of an element if a formula with a polyatomic ion has a coefficient.
2Mg(NO2)2
Figure out how many of the following are in ONE molecule
# of elements in ONE molecule ______
Number of atoms of each element in ONE molecule ____
Number of total atoms in ONE molecule ______
Number of molecules __1____
Figure out how many of the following are in TWO molecules
# of elements in TWO molecules ______
Number of atoms of each element in TWO molecules ____
Number of total atoms in TWO molecules ______
Number of molecules __2____
One molecule of 2Mg(NO2)2 Two molecules of 2Mg(NO2)2
# of elements in ONE molecule ___3___
Number of atoms of each element in ONE molecule
Mg-1 N-2 O-4
Number of total atoms in ONE molecule __7____
Number of molecules __1____
# of elements in TWO molecules ___3__(notice coefficient does not impact number of elements)
Number of atoms of each element in TWO molecules
Mg-1x2=2 N-2x2=4 O-4x2=8
Number of total atoms in TWO molecules _14_____
Number of molecules ___2___
Try this formula: 3Fe2(Cr2O7)3
Answers are below this table.
One molecule of 3Fe2(Cr2O7)3 Three molecules of 3Fe2(Cr2O7)3
# of elements in ONE molecule ______
Number of atoms of each element in ONE molecule
Number of total atoms in ONE molecule
Number of molecules __1____
# of elements in 3 molecules__(notice coefficient does not impact number of elements)
Number of atoms of each element in 3 molecules
Number of total atoms in 3 molecules _____
Number of molecules __3____
One molecule of 3Fe2(Cr2O7)3 Three molecules of 3Fe2(Cr2O7)3
# of elements in ONE molecule __3____
Number of atoms of each element in ONE molecule
Fe-2 Cr-6 O-21
Number of total atoms in ONE molecule__29__
Number of molecules __1____
# of elements in 3 molecules __3__(notice coefficient does not impact number of elements)
Number of atoms of each element in 3 molecules
Fe-2x3=6 Cr-6x3=18 O-21x3=63
Number of total atoms in 3 molecules _87____
Number of molecules __3____
When You Have Completed the Question Below, Click Next
2BaSO4 and 3Ba(OH)2 both have a similar white powder appearance, and have many of the same uses. What is the total number of oxygen atoms for both compounds?
6 Oxygen atoms
10 Oxygen atoms
11 Oxygen atoms
14 Oxygen atoms