Calculating Molecular Formula from Empirical Formula

Tyler DeWitt
28 Jun 201409:09
EducationalLearning
32 Likes 10 Comments

TLDRThis educational script teaches the method to determine the molecular formula of a compound from its empirical formula and molar mass. It demonstrates the process through an example, using CF2 with a molar mass of 200.04 g/mol, and explains how to multiply the empirical formula by a factor to match the given molar mass. The script also introduces a simplified calculation method to avoid making a chart for each problem, providing clear steps to find the molecular formula by dividing the compound's molar mass by the empirical formula's molar mass and applying the result to the empirical formula itself.

Takeaways
  • 🔍 The video is a tutorial on how to determine the molecular formula of a compound given its empirical formula and molar mass.
  • 📚 The empirical formula CF2 is used as an example to illustrate the process of finding the molecular formula.
  • 📉 The molar mass of the empirical formula CF2 is calculated to be 50.01 grams per mole by adding the atomic masses of carbon and fluorine.
  • 🔢 The concept of multiples of the empirical formula is introduced, showing how different molecular formulas can be derived by multiplying the empirical formula.
  • 🔎 A chart is used in the video to visually represent the relationship between the empirical formula, its multiples, and their corresponding molar masses.
  • 📈 The molar mass of a compound is found by multiplying the molar mass of the empirical formula by the same multiple used for the molecular formula.
  • 🧩 The video demonstrates a method to find the correct multiple for the empirical formula without having to create a chart each time.
  • 📝 An equation is presented: Divide the molar mass of the compound by the molar mass of the empirical formula to find the multiple.
  • 🤓 The process is applied to determine the molecular formula C4F8 for a compound with a molar mass of 200.04 grams per mole.
  • 📚 Additional examples are given to practice the method, including compounds with empirical formulas C2H2O, C2H5N, and CH3F.
  • 📉 The molar masses of the empirical formulas for these examples are calculated and used to find the multiples and the molecular formulas.
Q & A

  • What is the empirical formula and how is it used in determining the molecular formula of a compound?

    -The empirical formula represents the simplest whole number ratio of atoms in a compound. It is used to determine the molecular formula by multiplying the empirical formula by a certain factor until the calculated molar mass matches the given molar mass of the compound.

  • How do you calculate the molar mass of the empirical formula CF2?

    -You calculate the molar mass of the empirical formula CF2 by adding the molar mass of one carbon atom (approximately 12.01 g/mol) to twice the molar mass of a fluorine atom (approximately 19.00 g/mol), which gives a total of approximately 50.01 g/mol.

  • What is the difference between an empirical formula and a molecular formula?

    -An empirical formula shows the simplest ratio of elements in a compound, while a molecular formula represents the actual number of atoms of each element in a molecule of the compound, which can be a multiple of the empirical formula.

  • How can you find the molecular formula of a compound when given its empirical formula and molar mass?

    -You can find the molecular formula by dividing the given molar mass of the compound by the molar mass of the empirical formula, which gives you the factor by which you need to multiply the empirical formula.

  • What is the molecular formula of a compound with an empirical formula of CF2 and a molar mass of 200.04 g/mol?

    -The molecular formula of the compound is C4F8, as multiplying the empirical formula CF2 by 4 gives a molar mass of 200.04 g/mol.

  • Why is it necessary to multiply the empirical formula by a certain factor to find the molecular formula?

    -Multiplying the empirical formula by a certain factor is necessary because the empirical formula represents the simplest ratio of elements, and the actual molecular formula may have more atoms in the molecule, which can be determined by this multiplication.

  • Can you provide an example of how to calculate the molecular formula using the method described in the script?

    -Sure, for a compound with an empirical formula of C2H2O and a molar mass of 126.12 g/mol, you would first calculate the molar mass of the empirical formula (C2H2O = 2*12.01 + 2*1.01 + 16.00 = 42.04 g/mol), then divide the given molar mass by this value (126.12 / 42.04 = 3). Multiply the empirical formula by this factor to get the molecular formula: C6H6O3.

  • What is the molar mass of the empirical formula C2H5N and how is it used in determining the molecular formula?

    -The molar mass of the empirical formula C2H5N is calculated by adding the molar masses of 2 carbon atoms, 5 hydrogen atoms, and 1 nitrogen atom (2*12.01 + 5*1.01 + 14.01 = approximately 43.08 g/mol). This value is used to determine the molecular formula by dividing the given molar mass of the compound by this molar mass to find the multiplication factor.

  • How does the script simplify the process of finding the molecular formula without making a chart?

    -The script simplifies the process by using a direct calculation method where you divide the given molar mass of the compound by the molar mass of the empirical formula to find the multiplication factor, then multiply the empirical formula by this factor to get the molecular formula.

  • What is the molecular formula of a compound with an empirical formula of CHN and a molar mass of 86.16 g/mol?

    -By dividing the molar mass of the compound (86.16 g/mol) by the molar mass of the empirical formula CHN (approximately 43.08 g/mol), you get a factor of 2. Multiplying the empirical formula by this factor gives the molecular formula C2H6N2.

  • What is the molecular formula of a compound with an empirical formula of CH and a molar mass of 64.18 g/mol?

    -Dividing the molar mass of the compound (64.18 g/mol) by the molar mass of the empirical formula CH (approximately 13.01 g/mol) gives a factor of 4.93, which is rounded to 6 for simplicity. Multiplying the empirical formula by 6 gives the molecular formula C6H6.

Outlines
00:00
🔍 Determining Molecular Formula from Empirical Formula and Molar Mass

This paragraph explains the process of determining a compound's molecular formula given its empirical formula and molar mass. The example provided involves an empirical formula of CF2 with a molar mass of 200.04 g/mol. The speaker demonstrates how to calculate the molar mass of the empirical formula and then how to find multiples of this formula that match the given molar mass. The process involves multiplying the empirical formula by different integers to find a molecular formula with the exact molar mass. The correct molecular formula is identified as C4F8, which matches the molar mass of 200.04 g/mol. The speaker also introduces a simpler method for solving such problems without creating a chart, using a direct calculation to find the multiplier for the empirical formula.

05:00
📚 Simplified Method for Calculating Molecular Formulas

The second paragraph focuses on a simplified method for calculating molecular formulas when the empirical formula and the molar mass of a compound are known. The speaker provides several examples, including compounds with empirical formulas C2H2O, C2H5N, and CH3F. For each example, the molar mass of the compound is divided by the molar mass of the empirical formula to find the multiplier. This multiplier is then used to scale up the empirical formula to the molecular formula. The examples illustrate how to apply this method to determine the molecular formulas C6H6O3, C4H10N2, and C12H6F6, respectively. The paragraph emphasizes the efficiency of this approach in solving such problems without the need for extensive charts or tables.

Mindmap
Keywords
💡Empirical formula
The empirical formula is the simplest whole-number ratio of atoms present in a compound. It is a fundamental concept in the script as it serves as the starting point for determining the molecular formula of a compound. For instance, the script begins with the empirical formula 'CF2' to illustrate the process of finding the molecular formula.
💡Molar mass
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is a key concept in the script as it is used to distinguish between empirical and molecular formulas. The script uses the molar mass of 200.04 g/mol to identify the correct molecular formula that corresponds to the empirical formula 'CF2'.
💡Molecular formula
A molecular formula is a chemical formula that shows the exact number of atoms of each element in a molecule of a substance. The script's main objective is to demonstrate how to convert an empirical formula into a molecular formula using the molar mass as a guide, as seen with the progression from 'CF2' to 'C4F8'.
💡Periodic table
The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties. It is referenced in the script to find the molar masses of elements like carbon and fluorine, which are necessary to calculate the molar mass of the empirical formula.
💡Simplification
Simplification in the context of the script refers to the process of reducing the ratio of atoms in a compound to its simplest form, resulting in the empirical formula. The script mentions that the empirical formula 'CF2' is a simplified representation of the compound's atomic composition.
💡Multiples
In the script, multiples refer to the factor by which the empirical formula is multiplied to obtain a molecular formula with a specific molar mass. The concept is illustrated through examples like 'C2F4' and 'C3F6', which are multiples of the empirical formula 'CF2'.
💡Carbon
Carbon is an element with the symbol C and atomic number 6. It is a key element in organic chemistry and is mentioned in the script as part of the empirical formula 'CF2'. The molar mass of carbon is used in calculations to determine the molar mass of the empirical formula.
💡Fluorine
Fluorine is a highly reactive element with the symbol F and atomic number 9. It is paired with carbon in the empirical formula 'CF2' discussed in the script. The molar mass of fluorine is essential for calculating the molar mass of the empirical formula.
💡Calculation
Calculation is the process of determining something by mathematical reasoning. In the script, various calculations are performed to find the molar mass of empirical formulas and to determine the correct multiple that, when applied, results in the molecular formula with the given molar mass.
💡Method
The method described in the script is a systematic approach to solving problems related to determining molecular formulas from empirical formulas and molar masses. The script outlines both a chart method and a simplified equation-based method to achieve this goal.
Highlights

Introduction to solving problems involving empirical formulas and molar mass to determine molecular formulas.

The empirical formula CF2 is given with a molar mass of 200.04 grams per mole for determining the molecular formula.

Explanation of calculating the molar mass of the empirical formula CF2 as 50.01 grams per mole.

Concept of empirical formula as a simplified ratio of atoms in a compound.

Different molecular formulas can share the same empirical formula, such as C2F4 and C3F6 with CF2.

Demonstration of how to multiply the empirical formula to obtain different molecular formulas.

Identification of C4F8 as the molecular formula with the desired molar mass of 200.04 grams per mole.

The method of multiplying the empirical formula's molar mass to find the correct molecular formula.

Introduction of a simplified method to avoid creating a chart for each problem.

Using the molar mass of the molecular formula and dividing by the empirical formula's molar mass to find the multiplier.

Calculation of the molecular formula C4F8 by multiplying the empirical formula CF2 by 4.

Application of the simplified method to determine the molecular formula of a compound with empirical formula C2H2O and a molar mass of 126.12 grams per mole.

Calculation resulting in the molecular formula C6H12O3 for the compound with the given empirical formula and molar mass.

Determination of the molecular formula for a compound with empirical formula C2H5N and a molar mass of 86.16 grams per mole.

Resulting molecular formula C4H10N2 for the compound with the empirical formula C2H5N.

Example calculation for a compound with empirical formula CHN and a molar mass of 64.18 grams per mole.

Final molecular formula C12H6F6 determined for the compound with the given empirical formula and molar mass.

Transcripts

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