# How to solve sums related to empirical formula

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Step 1: Determine the elements given and write each separately followed by a colon with significant space between (as seen below H: … C: …)

Step 2: Determine the amounts of each element given and write the amount directly after the colon for each specific element. If the amounts are given in a percent; assume that you are dealing with a 100g sample and the percent would be the mass in grams (30% C is 30g C in a 100g sample).

Step 3: Convert the grams of each element to moles (elements not molecules…Oxygen in this case is not existing as a diatomic gas so its molar mass is 16.00g/mol, not 32g/mol)

Step 4: Divide each of the mole amounts by the smallest mole amount that you solved for. This will give you a ratio of 1 to something. You may have a exact whole number ratio at this point, if not continue to step 5

Step 5: If necessary multiply each of the values by prime numbers to determine the whole number ratio between atoms. (start with 2, if that doesn’t work try 3, or 5, or 7) If this doesn’t work you have a mistake somewhere.

Step 6: Write the empirical formula with the ratio as the number of each element. Remember the most metallic element always goes first. Hydrogen only goes first if the compound is identified as an acid.

Step 7: To solve for the Molecular Formula use the formula:

(Empirical Formula)n = Molecular Formula 