Empirical and Molecular Formula Flashcards
Define empirical formula.
The empirical formula is the chemical formula which represents the simplest whole number ratio of atoms in the compound.
Define molecular formula.
The molecular formula is the chemical formula which represents the actual formula of a compound.
The molecular formula of hydrogen peroxide is H2O2. What is the empirical formula?
HO is the empirical formula for hydrogen peroxide (H2O2).
HO is the empirical formula for hydrogen peroxide. What additional information would you need to determine the molecular formula?
Given the empirical formula (HO), one needs the molar mass to determine the molecular formula. In this case the molar mass for hydrogen peroxide is about 34 g/mol. Given the empirical formula mass is 17 g/mol and 34/17 = 2, the molecular formula is 2 x HO = H2O2.
The molecular formula of glucose is C6H12O6. What is the empirical formula?
CH2O is the empirical formula for glucose (C6H12O6).
CH2O is the empirical formula for glucose. What additional information would you need to determine the molecular formula?
Given the empirical formula (CH2O), one needs the molar mass to determine the molecular formula. In this case the molar mass for glucose is about 180 g/mol. Given the empirical formula mass is 30 g/mol and 180/30 = 6, the molecular formula is 6 x CH2O = C6H12O6.
The molecular formula of aspirin (acetylsalicylic acid) is C9H8O4. What is the empirical formula?
C9H8O4 is already the simplest whole number ratio and therefore this is the empirical formula.
What is the empirical formula for magnesium chloride?
The empirical formula for magnesium chloride is MgCl2. In this question we are not providing data to determine the empirical formula but rather we are asking you to predict the formula based on your knowledge of the charges of magnesium (Mg2+) and chloride (Cl-). Usually we would simply ask you to provide the “formula” for magnesium chloride.
