Calculating Mole Grade 10 | Part 1

Summary

This chemistry lesson focuses on calculating moles using the formula n = m/M, where n is the number of moles, m is the given mass, and M is the molar mass. Examples are provided for CO2, H2O, and H2SO4 to demonstrate how to find moles from mass and vice versa. The instructor also introduces a triangle method to rearrange the formula for different calculations, including determining mass from moles and molar mass.

Takeaways

• 🔍 The formula n = m/M is used to calculate the number of moles (n), where m is the given mass and M is the molar mass.
• 📚 The molar mass (M) is the mass of one mole of a substance, which can be found on the periodic table and is measured in grams per mole.
• 🧪 Examples are used to demonstrate how to calculate the number of moles in a given mass of a substance, such as CO2, H2O, and H2SO4.
• 📈 The molar mass of a compound is calculated by summing the atomic masses of all the atoms in the compound's formula.
• ⚖️ For CO2, the molar mass is calculated as 12 (carbon) + 2*16 (oxygen) = 44 grams per mole.
• 💧 For H2O, the molar mass is 2*1 (hydrogen) + 16 (oxygen) = 18 grams per mole.
• 🌊 For H2SO4, the molar mass is 2*1 (hydrogen) + 32 (sulfur) + 4*16 (oxygen) = 98 grams per mole.
• 🔄 The formula can be rearranged to solve for different variables, such as calculating mass when given moles or molar mass.
• 📉 The concept of a 'triangle' is introduced to help remember the relationships and rearrangements of the formula n = m/M.
• 🔢 Practice problems are provided to reinforce learning and apply the formula in various scenarios, including calculating mass from moles and vice versa.

Q & A

What does the formula n = m/M represent?

The formula n = m/M represents the relationship between the number of moles (n), the mass (m), and the molar mass (M) of a substance.

What is the difference between the lowercase 'm' and uppercase 'M' in the context of the formula?

In the formula, the lowercase 'm' represents the given mass of a substance, while the uppercase 'M' represents the molar mass of that substance.

How is the molar mass of CO2 calculated?

The molar mass of CO2 is calculated by adding the atomic mass of one carbon atom (12) and two oxygen atoms (16 each), resulting in a total of 44 grams per mole.

What is the molar mass of H2O?

The molar mass of H2O is calculated by adding the mass of two hydrogen atoms (1 each) and one oxygen atom (16), resulting in a total of 18 grams per mole.

How many moles are in 88 grams of CO2?

Using the formula n = m/M, and knowing the molar mass of CO2 is 44 grams per mole, there are 2 moles in 88 grams of CO2.

What is the molar mass of H2SO4?

The molar mass of H2SO4 is calculated by adding the mass of two hydrogen atoms (1 each), one sulfur atom (32), and four oxygen atoms (16 each), resulting in a total of 98 grams per mole.

How many moles are in 54 grams of H2O?

Using the formula n = m/M, and knowing the molar mass of H2O is 18 grams per mole, there are 3 moles in 54 grams of H2O.

How many moles are in 49 grams of H2SO4?

Using the formula n = m/M, and knowing the molar mass of H2SO4 is 98 grams per mole, there are 0.5 moles in 49 grams of H2SO4.

How can the formula n = m/M be rearranged to solve for mass (m)?

To solve for mass (m), the formula can be rearranged to m = n * M, where n is the number of moles and M is the molar mass.

How can the formula n = m/M be rearranged to solve for molar mass (M)?

To solve for molar mass (M), the formula can be rearranged to M = m/n, where m is the mass and n is the number of moles.

What is the mass of 3 moles of CO2?

Using the rearranged formula m = n * M, and knowing the molar mass of CO2 is 44 grams per mole, the mass of 3 moles of CO2 is 132 grams.