Chemistry Moles and Mass Quiz

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)

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.