Dimethylhydrazine, a colorless liquid used as a rocket fuel, is 40.0% C, 13.3% H, and 46.7% N. What is the empirical formula? (LO 3.11) (a) CH4N9 (b) CH2N (c) C2H4N (d) C2H5N2
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Assume you have 100 grams of dimethylhydrazine, which means you have 40.0 grams of carbon (C), 13.3 grams of hydrogen (H), and 46.7 grams of nitrogen (N).
Convert the mass of each element to moles by dividing by their respective molar masses: Carbon (C) is 12.01 g/mol, Hydrogen (H) is 1.008 g/mol, and Nitrogen (N) is 14.01 g/mol.
Calculate the moles of each element: \( \text{moles of C} = \frac{40.0}{12.01} \), \( \text{moles of H} = \frac{13.3}{1.008} \), \( \text{moles of N} = \frac{46.7}{14.01} \).
Determine the simplest whole number ratio of moles of each element by dividing each by the smallest number of moles calculated in the previous step.
Use the whole number ratios to write the empirical formula, ensuring that the subscripts in the formula are the smallest possible whole numbers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Empirical Formula
The empirical formula represents the simplest whole-number ratio of the elements in a compound. It is derived from the percentage composition of each element, allowing chemists to understand the basic composition of a substance without detailing the actual number of atoms in a molecule.
The mole concept is a fundamental principle in chemistry that relates the mass of a substance to the number of particles it contains. One mole of any substance contains Avogadro's number (approximately 6.022 x 10²³) of entities, whether they are atoms, molecules, or ions, facilitating conversions between mass and number of particles.
Percentage composition refers to the mass percentage of each element in a compound. It is calculated by dividing the mass of each element by the total mass of the compound and multiplying by 100. This information is crucial for determining the empirical formula, as it provides the necessary data to find the simplest ratio of elements.
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