Chemistry Period 8: Mrs. Fleming
Wednesday October 28th
Homework: Review Packet Q: 37-43 on loose-leaf. Show all
work!
Do Now:
1) Is C2H2 an empirical or molecular formula? How do you know?
2) What is the empirical formula of
a. C4H10 =
b. C2H6 =
c. Al2O3 =
3) Circle the empirical formulas
a. CH3
b. C2H6
c. Al2O3
d. C2H5Cl
e. C6H12O6
Students Will Be Able To (SWBAT): Calculate Molecular Formulas from Empirical Formulas
A compound has a molecular mass of 180 g/mol, and an empirical formula of CH2O. What is its molecular
formula?
Step 1: Determine the molecular mass of the empirical formula (CH2O). Show all work below
Step 2: Divide molecular mass by the mass of the empirical formula:
Molecular mass
Empirical mass
=
=
Step 3: Multiply the subscripts of the empirical formula by the ratio number found in step 2
ANSWER: _______________________________________
Not sure if you did it correctly? CHECK YOUR WORK! 1) Is the empirical formula of your answer = to CH2O?
2) Is the GMM of your answer 180 g/mol? CONGRATULATIONS!
Practice Questions:
1) A compound has a molecular mass of 78 g/mol and an empirical formula of CH. What is its
molecular formula?
2) A compound has a molecular mass of 56 g/mol and an empirical formula of CH2. What is its
molecular formula?
3) A compound has a molecular mass of 176 g/mol and an empirical formula of C3H4O3. What is its
molecular formula?
4) A compound has a molecular mass of 28 g/mol and an empirical formula of CH2. What is its
molecular formula?
5) A compound has a molecular mass of 30 g/mol and an empirical formula of CH3. What is its
molecular formula?