Percent Compositions of Compound| Grade 9 Science Quarter 2 Week 8 | DepEd MELC-based

Summary

In this educational video, students learn to calculate the percentage composition of compounds, using both real-life examples like instant coffee and chemical examples like ethanol. The lesson covers how to determine the mass percent of elements in a compound by dividing the mass of an element by the total mass of the compound and multiplying by 100%. The importance of percent composition in chemistry for analyzing substances and determining empirical formulas is highlighted. The video concludes with a reminder to practice and engage with the content.

Takeaways

• 📚 The lesson is focused on teaching students how to determine the percentage composition of compounds.
• 🔍 The concept of percentage composition is introduced with an analogy to exam scores and instant coffee ingredients.
• 📊 To calculate the percentage composition, the formula involves dividing the mass of an element by the mass of the compound and multiplying by 100%.
• 🧪 Practical applications of percentage composition include preparing solutions and verifying the purity of substances in a lab.
• 🍇 The example of ethanol (C2H6O) is used to demonstrate the calculation of mass percent for each element in a compound.
• 🧬 Ethanol's molar mass is calculated by summing the atomic masses of its constituent elements: carbon (2x12.01), hydrogen (6x1.008), and oxygen (1x16.00).
• 📉 The mass percent of each element in ethanol is calculated and then rounded to the nearest hundredth.
• 🔄 The sum of the mass percentages of all elements in a compound should total 100%, which can be used to check calculations.
• 📊 A pie chart is used to visually represent the mass percent composition of ethanol.
• 📝 The lesson concludes by emphasizing the importance of percent composition in analyzing and determining the empirical formula of a substance.

Q & A

What is the main topic of the lesson?

The main topic of the lesson is the calculation of the percentage composition of compounds.

What is an example given to explain percentage composition?

An example given is an instant coffee sachet which contains 10 grams of coffee, 13 grams of sugar, and 12 grams of milk, making a total of 35 grams.

How is the percentage composition of coffee in the instant coffee sachet calculated?

The percentage composition of coffee is calculated by dividing the mass of coffee (10 grams) by the total mass of the sachet (35 grams) and multiplying by 100, which results in approximately 28.57%.

What is the mass percent formula used in the laboratory?

The mass percent formula used in the laboratory is: mass percent = (mass of element / mass of compound) × 100%.

What is the chemical formula for ethanol mentioned in the script?

The chemical formula for ethanol is C2H6O.

How is the molar mass of ethanol calculated?

The molar mass of ethanol is calculated by adding the atomic masses of two carbon atoms (2 × 12.01 g/mol), six hydrogen atoms (6 × 1.008 g/mol), and one oxygen atom (16.0 g/mol), resulting in approximately 46.07 g/mol.

What is the mass percent of carbon in ethanol?

The mass percent of carbon in ethanol is approximately 52.14%, calculated by dividing the mass of carbon (24.02 g) by the molar mass of ethanol (46.07 g) and multiplying by 100.

How is the mass percent of hydrogen in ethanol determined?

The mass percent of hydrogen in ethanol is determined to be approximately 13.14% by dividing the mass of hydrogen (6.048 g) by the molar mass of ethanol (46.07 g) and multiplying by 100.

What is the mass percent of oxygen in ethanol?

The mass percent of oxygen in ethanol is approximately 34.73%, found by dividing the mass of oxygen (16.0 g) by the molar mass of ethanol (46.07 g) and multiplying by 100.

Why is it important to ensure that the sum of the mass percentages of all elements in a compound equals 100%?

Ensuring the sum of the mass percentages equals 100% is important as it verifies the accuracy of the calculations and confirms that all components of the compound have been accounted for.

What role does percent composition play in chemistry?

Percent composition is crucial in chemistry for analyzing and determining the empirical formula of a chemical substance.