Percent Composition, Empirical & Molecular Formulas

What is the percent by mass of sodium in NaCl?

(Na = 22.99g/mol, Cl = 35.45 g/mol)

• 39%
• 61%
• 35%
• 65%

What is the percent by mass of fluorine in CaF₂?

(Ca = 40.08 g/mol, F = 19.00 g/mol)

• 24%
• 49%
• 51%
• 65%

An empirical formula:

• is a formula that calculates the coefficients of a compound in a balanced equation.
• is the simplest whole-number ratio of moles of elements in the compound.

What is the empirical formula of the following molecular formula:  C₃H₆

• C₃H₆
• CH₂
• C₂H₄
• CH₃

Which pair has the same empirical formula?

• NaCrO₄ and Na₂Cr₂O₇
• C₂H₄O₂ and C₆H₁₂O₆
• C₃H₆O₃ and C₂H₆O₂
• CH₄ and C₂H₆

What is the empirical formula for the following:
Pb₅Cr₅O₂₀

• Pb₂Cr₂O₁₀
• PbCr₂O₇
• Pb₉Cr₄O₂
• PbCrO₄

What is the empirical formula if you have 88.80% copper and 11.20% oxygen?

(Cu = 63.55 g/mol, O = 16.00 g/mol)

• Cu₃O₈
• CuO₄
• Cu₂O
• Cu₄O₁₀

You are given the following percentages: 40.05% S and 59.95% O.

(S = 32.07 g/mol, O = 16.00 g/mol)

Find the empirical formula for these elements so that you can give the correct name of the compound formed.

• Sulfur monoxide

• Sulfur dioxide

• Sulfur trioxide

• Sulfur tetroxide

A chemical formula that shows the actual number and kinds of atoms present in one molecule of a compound is called_________

• ionic formula
• covalent formula
• empirical formula
• molecular formula

What is the molecular formula if the empirical formula is CH₂O and the molecular molar mass is 180.18?

(C = 12.01 g/mol, H = 1.01 g/mol, O = 16.00 g/mol)

• CH₂O
• C₂H₄O₂
• C₄H₈O₄
• C₆H₁₂O₆