Percent Composition By Mass

Tyler DeWitt
16 Jun 201406:58
EducationalLearning
32 Likes 10 Comments

TLDRThis educational video script teaches viewers how to calculate the percent composition by mass of elements in a compound. It demonstrates the process using water (H2O), iron chloride (FeCl3), and a large organic compound (C6H1000) as examples. The script explains the formula for percent composition, involves looking up molar masses on the periodic table, and shows the steps to find the molar mass of the compound and the element of interest. The method involves dividing the total molar mass of the element by the molar mass of the compound, then multiplying by 100% to get the final percentage.

Takeaways
  • 🧪 The script teaches how to calculate the percent composition by mass of an element in a compound.
  • 📚 Percent composition by mass is also referred to as 'percent by mass' and they are used interchangeably.
  • 🔢 The formula for calculating percent composition by mass involves dividing the total molar mass of the element by the molar mass of the whole compound and multiplying by 100%.
  • 🌐 To find the molar mass of a compound, sum the molar masses of all the elements present in the compound as indicated by their chemical formula.
  • 💧 For water (H2O), the molar mass is calculated by adding twice the molar mass of hydrogen (2 x 1.01) to the molar mass of oxygen (1 x 16.00), resulting in 18.02 g/mol.
  • 🔍 The percent composition by mass of hydrogen in H2O is found by dividing the total molar mass of hydrogen (2.02) by the molar mass of water (18.02) and multiplying by 100%, yielding approximately 11.2%.
  • 🌟 The process is demonstrated with other compounds such as FeCl3, where the molar mass of iron is compared to the total molar mass of the compound to find the percent composition by mass of iron.
  • ⚗️ For C6H1000O4, the molar mass of just the carbon atoms is calculated by multiplying the number of carbon atoms by the molar mass of a single carbon atom, and then divided by the total molar mass of the compound to find the percent composition by mass of carbon.
  • 📈 The script emphasizes the importance of using significant figures in calculations and rounding results appropriately.
  • 📝 The video script provides a step-by-step guide on how to perform these calculations, including looking up molar masses on the periodic table and performing the necessary arithmetic operations.
  • 🔬 The concept is applicable to various chemical compounds, not just the examples provided, making it a fundamental skill in chemistry.
Q & A

  • What is percent composition by mass?

    -Percent composition by mass is a way to express the proportion of each element in a compound by its mass. It is calculated by dividing the total molar mass of an individual element by the molar mass of the entire compound and then multiplying by 100%.

  • What is the formula for calculating percent composition by mass?

    -The formula for calculating percent composition by mass is (Total molar mass of the element / Molar mass of the compound) × 100%.

  • How do you calculate the molar mass of H2O?

    -You calculate the molar mass of H2O by adding the molar masses of two hydrogen atoms (2 × 1.01 g/mol) and one oxygen atom (1 × 16.00 g/mol), which gives a total of 18.02 g/mol.

  • What is the percent composition by mass of hydrogen in H2O?

    -The percent composition by mass of hydrogen in H2O is approximately 11.2%, calculated by dividing the total molar mass of hydrogen (2.02 g/mol) by the molar mass of H2O (18.02 g/mol) and multiplying by 100%.

  • How do you find the molar mass of a compound like FeCl3?

    -To find the molar mass of FeCl3, you sum the molar masses of one iron atom (55.85 g/mol) and three chlorine atoms (3 × 35.45 g/mol), resulting in a total molar mass of 162.20 g/mol.

  • What is the percent composition by mass of iron in FeCl3?

    -The percent composition by mass of iron in FeCl3 is approximately 34.43%, which is found by dividing the molar mass of iron (55.85 g/mol) by the molar mass of FeCl3 (162.20 g/mol) and multiplying by 100%.

  • How do you calculate the molar mass of a compound with multiple elements, such as C6H10O4?

    -You calculate the molar mass of C6H10O4 by adding the molar masses of six carbon atoms (6 × 12.01 g/mol), ten hydrogen atoms (10 × 1.01 g/mol), and four oxygen atoms (4 × 16.00 g/mol), giving a total molar mass of 146.20 g/mol.

  • What is the percent composition by mass of carbon in C6H10O4?

    -The percent composition by mass of carbon in C6H10O4 is approximately 49.29%, calculated by dividing the total molar mass of carbon (72.06 g/mol) by the molar mass of the compound (146.20 g/mol) and multiplying by 100%.

  • Why is it important to round the results to significant figures in calculations?

    -Rounding to significant figures ensures that the precision of the result matches the precision of the measurements or calculations involved, avoiding misleading precision.

  • Can you use the same process to calculate the percent composition by mass for any element in any compound?

    -Yes, the process of calculating the percent composition by mass is universal and can be applied to any element in any compound by following the formula: (Total molar mass of the element / Molar mass of the compound) × 100%.

Outlines
00:00
🧪 Calculating Percent Composition by Mass

This paragraph introduces the concept of calculating the percent composition by mass, specifically focusing on the element hydrogen in the compound H2O. The process involves using a formula that compares the total molar mass of the element of interest to the molar mass of the entire compound. The molar mass of water (H2O) is calculated by adding the molar masses of two hydrogen atoms (2 x 1.01) and one oxygen atom (16.00), resulting in 18.02. The percent composition is then found by dividing the total molar mass of hydrogen by the molar mass of water and multiplying by 100%, yielding 11.2% for hydrogen in H2O.

05:02
📚 Advanced Percent Composition Examples

The second paragraph delves into more complex examples of calculating percent composition by mass, such as for the compound FeCl3 and a large organic molecule, C6H1000. The process involves determining the molar mass of the entire compound and the molar mass of the element of interest within it. For FeCl3, the molar mass is calculated by adding the molar mass of one iron atom (55.85) and three chlorine atoms (3 x 35.45), resulting in 162.20. The percent composition by mass of iron is then calculated, yielding 34.03%. For the large organic molecule, the molar mass of carbon is calculated by multiplying the number of carbon atoms (6) by the molar mass of a single carbon atom (12.01), and then dividing by the total molar mass of the compound (146.2), resulting in a percent composition by mass of 49.29% for carbon.

Mindmap
Keywords
💡Percent Composition by Mass
Percent composition by mass is a method used in chemistry to determine the percentage of each element in a compound by weight. It is essential for understanding the proportions of elements in a substance. In the video, this concept is used to calculate the percentage of hydrogen in H2O, iron in FeCl3, and carbon in C6H1000, showing how to apply the formula to different compounds.
💡Molar Mass
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in a molecule or formula unit of a compound. In the script, molar mass is used to find the total mass of elements in a compound, such as the molar mass of H2O, FeCl3, and C6H1000, which is crucial for determining percent composition by mass.
💡Hydrogen
Hydrogen is the first element in the periodic table with an atomic number of 1 and an atomic mass of approximately 1.01 g/mol. In the video, hydrogen's molar mass is used to calculate its percent composition in water (H2O), emphasizing its importance in the compound's overall mass.
💡Oxygen
Oxygen is a chemical element with the symbol O and atomic number 8. It has an atomic mass of approximately 16.00 g/mol. In the context of the video, oxygen's molar mass is combined with that of hydrogen to determine the molar mass of water, highlighting its role in the compound's structure.
💡Iron
Iron, with the symbol Fe, is a metal in the first transition series of the periodic table. It has an atomic mass of about 55.85 g/mol. The script uses iron's molar mass to calculate its percent composition in the compound FeCl3, illustrating how to apply the concept to metals.
💡Chlorine
Chlorine is a nonmetal with the symbol Cl and atomic number 17. It has an atomic mass of approximately 35.45 g/mol. In the video, chlorine's molar mass is multiplied by three to account for the three chlorine atoms in FeCl3, showing how to calculate the molar mass of a compound with multiple atoms of the same element.
💡Carbon
Carbon is a nonmetal with the symbol C and atomic number 6. It has an atomic mass of about 12.01 g/mol. The script calculates the molar mass of carbon in the compound C6H1000 by multiplying the atomic mass of carbon by six, demonstrating the calculation process for compounds with multiple atoms of the same element.
💡Significant Figures
Significant figures are the digits in a number that carry meaning contributing to its precision. The video emphasizes the importance of rounding results to the correct number of significant figures, as seen when calculating the percent composition of hydrogen in H2O, to maintain the accuracy of the results.
💡Chemical Formula
A chemical formula represents the composition of a compound, indicating the elements present and their proportions. The script uses chemical formulas like H2O, FeCl3, and C6H1000 to determine the number of atoms of each element, which is necessary for calculating molar mass and percent composition by mass.
💡Periodic Table
The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties. The video script refers to the periodic table to look up the atomic masses of elements like hydrogen, oxygen, iron, chlorine, and carbon, which are needed to calculate molar masses and percent compositions.
Highlights

Introduction to calculating percent composition by mass.

Explanation of the formula for calculating percent composition by mass.

Clarification that percent composition by mass is the same as percent by mass.

Process of dividing the molar mass of an element by the molar mass of the compound to find the percentage.

How to calculate the molar mass of water (H2O) by adding the molar masses of hydrogen and oxygen.

The molar mass of water is determined to be 18.02 g/mol.

Calculation of the total molar mass of hydrogen in water.

Using the formula to find the percent composition by mass of hydrogen in H2O, resulting in 11.2%.

Moving on to calculate the percent by mass of iron in FeCl3.

Determining the molar mass of FeCl3 by adding the molar masses of iron and chlorine.

The molar mass of iron in FeCl3 is calculated to be 55.85 g/mol.

Finding the percent by mass of iron in FeCl3 to be 34.43%.

Exploring the percent by mass of carbon in C6H1000.

Calculating the molar mass of the entire compound C6H1000.

Determining the molar mass of just the carbon atoms in C6H1000.

The percent by mass of carbon in C6H1000 is found to be 49.29%.

Summary of the method to calculate percent composition by mass for various compounds.

Transcripts

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ChemistryPercent CompositionMolar MassHydrogenOxygenWaterIronFeCl3CarbonC6H1000Educational