Chem 9-3 Emp and Molecular Formulas

Multiple Choice

Why is it important to understand both empirical and molecular formulas when studying chemical compounds?

• Because they help identify the physical properties of compounds

• Because they provide information about the composition and structure of compounds

• Because they are only used in laboratory experiments

• Because they are not related to chemical reactions

Open Ended

How does the molecular formula of a compound differ from its structural formula, and why might both be useful in chemistry?

Multiple Choice

Which of the following formulas for glucose is an empirical formula?

• C6H12O6

• CH2O

• H2O

• C2H4O2

Multiple Choice

Which of the following best describes the difference between an empirical formula and a molecular formula?

• Empirical formula shows the exact number of atoms in a molecule, molecular formula shows the simplest ratio.

• Empirical formula shows the simplest whole number ratio of atoms, molecular formula shows the actual number of atoms in a molecule.

• Empirical formula shows the structure of a molecule, molecular formula shows the mass percent.

• Empirical formula shows the percent composition, molecular formula shows the structure.

Open Ended

Explain how the structural formula provides more information about a compound compared to the empirical and molecular formulas.

Fill in the Blank

Scientists use two ways to describe what a compound is made of: the molecular formula and the ___ composition of a compound.

Multiple Choice

Given the molar masses of carbon, hydrogen, and oxygen in acetic acid (C2H4O2), what is the mass percent of hydrogen?

• 6.71%

• 40.00%

• 53.29%

• 12.01%

Open Ended

What steps are involved in calculating the mass percent of each element in a compound such as acetic acid?

Multiple Choice

What is the first step scientists take to determine the empirical formula of a mystery compound using percent composition by mass?

• Weigh the sample and decompose it into its elements

• Calculate the number of moles of each element

• Find the smallest whole-number ratio of atoms

• Multiply the subscripts by n

Open Ended

Explain how percent composition by mass is used to determine the empirical formula of a compound.

Fill in the Blank

Calculate the number of moles of each element in the sample.

Fill in the Blank

The compound sample’s total mass is 50.00 grams. After the compound is decomposed, 41.33 g of carbon and 8.67 g of hydrogen are produced. Determine the empirical formula from the mystery compound.

Multiple Select

Which of the following steps are involved in calculating the percent composition and empirical formula of a compound?

• Divide each element's mass by the total sample mass

• Multiply the subscripts by n

• Calculate the number of moles of each element

• Find the smallest whole-number ratio of atoms

Multiple Choice

What is the relationship between the empirical formula and the molecular formula?

• The molecular formula is always the same as the empirical formula

• The molecular formula is a whole-number multiple of the empirical formula

• The empirical formula is always a whole-number multiple of the molecular formula

• The empirical formula and molecular formula are unrelated

Multiple Choice

Which two pieces of information are necessary to determine the molecular formula of a compound?

• Empirical formula and molar mass

• Empirical formula and melting point

• Molar mass and boiling point

• Empirical formula and density

Fill in the Blank

The value of n in the formula (Empirical formula mass * n = Molar Mass) for the given example is ___

Multiple Select

Which of the following steps are involved in determining the molecular formula from the empirical formula?

• Divide the molar mass by the empirical formula mass

• Multiply each subscript in the empirical formula by n

• Add the atomic masses of all elements

• Subtract the empirical formula mass from the molar mass

Open Ended

Explain the process of determining the molecular formula from the empirical formula and molar mass, using the example provided in the images.

Open Ended

Reflecting on today’s lesson about chemical formulas, what questions do you still have or what would you like to learn more about regarding molecular and empirical formulas?

Multiple Choice

How does the molecular formula differ from the empirical formula for glucose?

• The molecular formula shows the exact number of atoms in a molecule, while the empirical formula shows the simplest whole-number ratio of atoms.

• The molecular formula shows only the types of atoms present, while the empirical formula shows the structure.

• The molecular formula is always simpler than the empirical formula.

• The empirical formula is used in chemical equations, while the molecular formula is not.