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Questions and Answers
How many atoms are present in 2.50 mol of aluminum (Al)?
How many atoms are present in 2.50 mol of aluminum (Al)?
What is the molar mass of potassium hydroxide (KOH)?
What is the molar mass of potassium hydroxide (KOH)?
How many moles are in 2.85 g of calcium carbide (CaC2)?
How many moles are in 2.85 g of calcium carbide (CaC2)?
What does the term 'molar mass' refer to?
What does the term 'molar mass' refer to?
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If a mole of hydrochloric acid (HCl) has a mass of 36.46 g, what is the molar mass of individual H and Cl atoms represented in the calculation?
If a mole of hydrochloric acid (HCl) has a mass of 36.46 g, what is the molar mass of individual H and Cl atoms represented in the calculation?
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Which of the following represents Avogadro's number?
Which of the following represents Avogadro's number?
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How is the average atomic mass of an element determined?
How is the average atomic mass of an element determined?
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What quantity is equivalent to 1 mole of any substance?
What quantity is equivalent to 1 mole of any substance?
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Study Notes
Dimensional Analysis, Moles and Mass
- Dimensional analysis is used to connect introductory mole activity calculations
- Mole calculations involve converting between mass, moles, and representative particles (atoms, molecules, formula units)
Mole Practice Problems
- Show all work and unit cancellation for each problem.
- Example calculation: Determine the number of atoms in 2.50 moles of aluminum.
- Example calculation: How many moles are in 3.58 x 1023 formula units of ZnCl2?
Lab Tie In
- One mole of an element has a mass equal to its atomic mass in grams.
- Boron (B) has a molar mass of 10.8 g/mol.
- One mole of a compound has a mass equal to the sum of the atomic masses of its constituent elements.
- HCl has a molar mass of 36.46 g/mol (1.01 g/mol H + 35.45 g/mol Cl).
- Molar mass is the mass in grams of one mole of a substance.
Why Does This Work?
- Atomic mass units (amu) are based on the number of protons and neutrons in an atom.
- Carbon-12 is the standard for atomic mass (6 protons + 6 neutrons).
- Average atomic mass on the periodic table is calculated from the abundance of different isotopes.
- Average atomic mass is not always a whole number.
Moles and Carbon-12
- Moles are defined based on the number of atoms in 12 grams of Carbon-12.
- Avogadro's number (6.02 x 1023) represents the number of atoms in one mole.
The Point of Moles
- 6.02 x 1023 representative particles equals one mole
- One mole equals the molar mass of a representative particle.
- Moles are used to convert between mass, representative particles, and moles.
- Conversion factors include 1 mole/6.02 x 1023 representative particles and molar mass/1 mole.
- Molar mass is equal to the atomic mass in grams.
Let's Practice (Examples)
- Example 1: Calculate the molar mass of KOH. (Sum of atomic masses: 39.10 g/mol K + 16.00 g/mol O + 1.01 g/mol H = 56.11 g/mol KOH).
- Example 2: Determine the number of moles in 2.85 g of CaCl2. (Calculate molar mass of CaCl2 and use the conversion factor: 2.85g CaCl2 x 1mol/64.1g = 0.0445 mol CaCl2)
- Example 3: Calculate the mass of 1.32 moles of Ca. (Use the molar mass of calcium: 1.32 mol x 40.08 g/mol = 52.9 g Ca)
- Example 4: How many atoms are in 4.6 g of silver? (4.6 g Ag x 1 mol Ag/107.87 g Ag x 6.02 x 1023 atoms/1 mol = 2.6 x 1022 atoms).
Additional Mole Practice
- Example: Find the mass of 1.60 x 1024 atoms of Mn. (1.60 x 1024 atoms Mn x 1 mol/6.02 x 1023 atoms x 54.94 g/mol = 146 g Mn)
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Description
Test your understanding of dimensional analysis, moles, and mass in chemistry. This quiz includes practice problems that involve converting between mass, moles, and representative particles. Understand how to apply these concepts to real-world examples and lab scenarios.
