Formic acid is responsible for the sting of ant bites. By mass, formic acid is 26.10% C, 4.38% H, and 69.52% O. The molar mass of formic acid is 46.02 g/mol. Determine the molecular formula of formic acid and draw its Lewis structure.

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Step 1: Assume you have 100 g of formic acid, which allows you to directly convert the percentage composition to grams: 26.10 g of C, 4.38 g of H, and 69.52 g of O.

Step 2: Convert the mass of each element to moles by dividing by their respective atomic masses: C (12.01 g/mol), H (1.008 g/mol), and O (16.00 g/mol).

Step 3: Determine the simplest whole number ratio of moles of each element by dividing each by the smallest number of moles calculated in Step 2.

Step 4: Use the simplest whole number ratio to write the empirical formula of formic acid.

Step 5: Calculate the empirical formula mass and compare it to the given molar mass (46.02 g/mol) to find the molecular formula. Then, draw the Lewis structure based on the molecular formula, ensuring all atoms satisfy the octet rule where applicable.

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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. To determine it, the percentage composition of each element is converted to moles, and then the mole ratios are simplified. For formic acid, the empirical formula can be derived from its mass percentages of carbon, hydrogen, and oxygen.

Molecular Formula

The molecular formula indicates the actual number of atoms of each element in a molecule of a compound. It can be derived from the empirical formula by comparing the molar mass of the compound to the molar mass of the empirical formula. In the case of formic acid, knowing its molar mass allows us to determine how many times the empirical formula fits into the molecular formula.

Lewis Structure

A Lewis structure is a diagram that represents the bonding between atoms in a molecule and the lone pairs of electrons. It helps visualize the arrangement of electrons and the connectivity of atoms. For formic acid, drawing the Lewis structure involves placing the correct number of valence electrons around the carbon, hydrogen, and oxygen atoms to satisfy the octet rule where applicable.

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