Empirical Formula & Molecular Formula Determination From Percent Composition
The Organic Chemistry Tutor・6 minutes read
The text discusses how to determine the empirical and molecular formulas of compounds by converting mass percentages to grams, calculating moles of each element, and then dividing by the smallest value to find the formulas accurately. The process involves converting percentages to grams, calculating moles for each element, determining the empirical formula by dividing by the smallest value, and finally finding the molecular formula by dividing the molar mass of the compound by the molar mass of the empirical formula.
Insights
- The first compound analyzed has an empirical formula of C2H6 and a molecular formula of C6H18O3.
- The second compound studied has an empirical formula of C3H9N and a molecular formula of C12H36N4.
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Recent questions
How do you calculate moles from percentages?
Divide grams by atomic masses to find moles.
What is the empirical formula based on moles?
Divide moles by smallest value to determine empirical formula.
How do you find the molecular formula from the empirical formula?
Divide compound's molar mass by empirical formula's molar mass.
How do you convert grams to moles for elements?
Divide grams by respective atomic masses.
What is the significance of the smallest value in determining empirical formula?
The smallest value is used to find the simplest whole-number ratio.
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Summary
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Molecular Formulas Calculated from Elemental Composition
- Compound composed of 52.14% carbon, 13.13% hydrogen, and 34.73% oxygen by mass; convert percentages to grams based on 100 grams of compound.
- Calculate moles of carbon (4.34), hydrogen (13.026), and oxygen (2.171) by dividing grams by respective atomic masses.
- Determine empirical formula by dividing moles by smallest value (oxygen) to get C2H6 as the empirical formula.
- To find molecular formula, calculate molar mass of empirical formula (46.068), then divide molar mass of compound (138.204) by empirical formula's molar mass to get 3, resulting in C6H18O3 as the molecular formula.
- Another compound with 20.32g carbon, 5.12g hydrogen, and 7.9g nitrogen; convert grams to moles for each element.
- Calculate moles of carbon (1.692), hydrogen (5.079), and nitrogen (0.5639) by dividing grams by respective atomic masses.
- Determine empirical formula by dividing moles by smallest value (nitrogen) to get C3H9N as the empirical formula.
- Find molecular formula by dividing molar mass of compound (236.448) by empirical formula's molar mass (59.112) to get 4, resulting in C12H36N4 as the molecular formula.
