04/11: The Mole

• Chemistry
• Secondary Education

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CHEMISTRY 10

21: The Mole and the Avogadro constant 

Week 13

W E L C O M E !       Today is the 4th of November, 2024.

• Where will you put your learning materials: notebook, coursebook, pen and pencil, and fully-charged laptop?
  
• Have you kept your phone in your locker?
• Have you gone to the bathroom before the class starts?
• Have you checked any announcements or missing work on our Google Classroom?
• Are you seated in your assigned chair?

• define what a mole is.
• calculate the (a) amount of substance, (b) mass, (c) molar mass, (d) relative atomic mass or relative molecular / formula mass, and (e) number of particles using the value of the Avogadro constant.

• Which is easier to count: A or B ?

Which is easier to count: A or B ?

• Which is easier to count: A or B ?

• Which is easier to count: A or B ?

Mole (symbol: mol)

• amount of substance that contains as many particles (atoms, molecules, ions formula units, or electrons) as precisely 12 g of carbon-12.

How many atoms are there in each mass of element?

Molar Mass (symbol: Mr)

• the mass, in grams, of 1 mole of a substance

• How would you calculate the number of particles in a given mole?

• How would you calculate the number of particles in a given mole?

Sample

• 2Mg (s) + O2 (g) → 2MgO (s)

Strategy:

• 2Mg = 2 x (6.02 x 10²³ atoms) =  1.20x10²⁴ atoms
• 1O2 = 1 x (6.02 x 10²³ molecules) = 6.02 x 10²³ molecules
• 2MgO = 2 x (6.02 x 10²³ formula units) = 1.20x10²⁴ formula units
• 2Mg²⁺ = 2 x (6.02 x 10²³ Mg²⁺ cations) = 1.20x10²⁴ Mg²⁺ cations
• 2O²⁻ = 2 x (6.02 x 10²³ O²⁻ anions) = 1.20x10²⁴ O²⁻ anions

Guided Practice

• Continue on page 10 of your learning module.
• Study the sample question.
• Do (a) to (e).
• If you have any questions, please raise your hand.

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CHEMISTRY 10

21: The Mole and the Avogadro constant 

Week 13

Think about these:

• 1 mole of CO₂ = 6.02 x 10²³ molecules
• 1 mole of CO₂ = 44.0 g
• 44.0 g of CO₂ has 6.02 x 10²³ molecules

How many carbon dioxide molecules and moles are in 22.0 g of carbon dioxide?

Sample

• A flask contains 0.750 mol of carbon dioxide gas, CO₂. What mass of carbon dioxide gas is in this sample?

Strategy:

CO₂ n = 0.750 mol

CO₂ Mᵣ = ?    C = 12.0 g ; O₂ = 2 x 16.0                   Total Mᵣ = 12.0 + 32.0 = 44.0 g / mol

CO₂ m = ?

CO₂ m = n x Mᵣ

CO₂ m = 0.750 mol x 44.0 g / mol

CO₂ m = 33.0 g

                                                   Answer: The mass of 0.75 mol of carbon dioxide is 33.0 g.

Guided Practice

• Continue on pages 13-14 of your learning module.
• Study the sample question.
• Do (Activity 4) to (Activity 5).
• If you have any questions, please raise your hand.

Share your thought process.

I can define what a mole is.

Yes, I can confidently do it.

Yes, I can but need more practice.

No, I lack confidence so I need more practice or ask help from my teacher.

I can calculate the (a) amount of substance, (b) mass, (c) molar mass, (d) relative atomic mass or relative molecular / formula mass, and (e) number of particles using the value of the Avogadro constant.

Yes, I can confidently do it.

Yes, I can but need more practice.

No, I lack confidence so I need more practice or ask help from my teacher.

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STEM Project

Building a Futuristic City Scale Model

Week 11