Log in
Sign up for FREE
arrow_back
Library
Copy of Percent Comp Review (5/28/2026)
By Jason Poe
star
star
star
star
star
Share
share
Last updated about 2 hours ago
8 questions
Add this activity
1
1
3
1
1
1
1
Part of this formative will be performed as class, in which we will review how to do each part of the percent composition formula.
Please listen, participate, try your best, be open to making mistakes and learning from them.
H
2
O
Atomic Masses:
H = 1.008 g/mol
O = 16.00 g/mol
Total Mass of each element:
H = 2 atoms H (1.008) = 2.016 g/mol
O = 1 atom O (16.00) = 16.00 g/mol
Molar Mass of H
2
O:
2.016 + 16.00 = 18.016 g/mol
Question 1
1.
Question 2
2.
Question 3
3.
Mg
2
SO
4
To find the total mass of each element, I must identify two things:
a.) The atomic mass of each element in the molecule.
Mg _______
S _______
O _______
b.) The number of each element in the molecule.
Mg _______
S _______
O _______
Total mass of:
Mg _______ S _______ O _______
Include the units (g/mol).
Question 4
4.
Question 5
5.
Mg
2
SO
4
Total Mass of Each Element:
Mg = 24.31 g/mol
S = 32.06 g/mol
O = 64.00 g/mol
Molar Mass of Mg
2
SO
4
_______
Include the units (g/mol).
Question 6
6.
Below is an incomplete percent composition formula.
1
Question 8
8.
Total Mass of Each Element:
Mg = 24.31 g/mol
S = 32.06 g/mol
O = 64.00 g/mol
Molar Mass Mg
2
SO
4
: 120.37 g/mol
Determine the percent composition for each element in Mg
2
SO
4
. Include the units (%).
Round to nearest hundredth.
Mg = _______
S = _______
O = _______
Now, use what you have (hopefully) learned to complete percent composition 2 (link below).
Percent Comp 2 - https://app.formative.com/formatives/65c9a0e256d2b6644d116fa3
To find the total mass of an element in a molecule, what two things do I need (select all that apply)?
The number of molecules of the compound and the atomic mass of the element.
The number of atoms of the element in the molecule.
The total number of atoms in the molecule.
The molar mass of the molecule.
The atomic mass of the element from the periodic table.
Which of the following formula is correct for calculating the total mass of an element in a molecule (select all that apply)?
Total mass = (Molecular weight of the compound) ÷ (Number of atoms of the element)
Total mass = (Total mass of the molecule) + (Atomic mass of the element)
Total mass = (Number of atoms of the element) × (Atomic mass of the element)
Total mass = (Number of atoms of the element) + (Molecular weight of the compound)
Which of the following formula would you use to calculate the molar mass of a molecule (select all that apply)?
Molar mass = (Total mass of the compound) ÷ (Number of molecules)
Molar mass = (Add all the total masses of all elements in the molecule)
Molar mass = (Number of atoms of each element) × (Molecular weight of the compound)
Molar mass = (Atomic mass of the heaviest element) + (Number of elements in the molecule)
To find the percent composition for each element in Mg
2
SO
4
, which formula would I use (select all that apply)?
Question 7
7.
a.) In the percent composition formula to the left, define the following:
x = _______
y = _______
b.) What mathematical operation would I perform between x and y? _______
c.) What mathematical operation would I perform between the answer to (x/y) and 100? _______