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Questions and Answers
What is the volume of one mole of a gas at standard temperature and pressure?
What is the volume of one mole of a gas at standard temperature and pressure?
What is the number of atoms, molecules, or ions in one mole of a substance?
What is the number of atoms, molecules, or ions in one mole of a substance?
What is the standard pressure at standard temperature and pressure?
What is the standard pressure at standard temperature and pressure?
What is the definition of a mole of a substance?
What is the definition of a mole of a substance?
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What is the number of atoms in 12g of ¹²C?
What is the number of atoms in 12g of ¹²C?
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What is the symbol for relative atomic mass?
What is the symbol for relative atomic mass?
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How many atoms are there in 0.15moles of methane (CH₄)?
How many atoms are there in 0.15moles of methane (CH₄)?
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What is the relative atomic mass of Magnesium?
What is the relative atomic mass of Magnesium?
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What is the number of moles in a sample of oxygen containing 1.5 × 10²² molecules?
What is the number of moles in a sample of oxygen containing 1.5 × 10²² molecules?
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What is the molar mass of calcium chloride (CaCl₂)?
What is the molar mass of calcium chloride (CaCl₂)?
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How many moles are in 180g of water?
How many moles are in 180g of water?
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What is the molar mass of water (H₂O)?
What is the molar mass of water (H₂O)?
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What is the volume of 0.025 moles of N₂ at standard temperature and pressure?
What is the volume of 0.025 moles of N₂ at standard temperature and pressure?
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How many molecules are in 0.75 moles of Na?
How many molecules are in 0.75 moles of Na?
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Study Notes
Avogadro's Law
- Equal volumes of gases, under the same conditions of temperature and pressure, contain equal numbers of molecules.
- 1 mole of a gas at standard temperature and pressure (s.t.p) occupies a volume of 22.4L or 22,400cm³.
Moles and Molar Mass
- Moles: a mole of a substance is the amount of that substance that contains as many particles (atoms, molecules, or ions) as there are atoms of ¹²C in 12g of ¹²C.
- Molar Mass (Mr): the mass of 1 mole of a substance, usually expressed in units of g/mol.
- Formula: Moles x Mr = Mass (in grams)
Conversions
- Moles to Mass: Moles x Mr = Mass (in grams)
- Moles to Volume: Moles x 22.4 = Volume (in liters) at s.t.p
- Mass to Moles: Mass ÷ Mr = Moles
- Volume to Moles: Volume ÷ 22.4 = Moles at s.t.p
Standard Temperature and Pressure (s.t.p)
- Standard Temperature: 273K
- Standard Pressure: 101325 Pa
The Mole (mol)
- A mole is the unit for the amount of a substance, defined as the amount of a substance that contains as many particles (atoms, molecules, or ions) as there are atoms of ¹²C in 12g of ¹²C.
- Avogadro's Number (L) is 6 × 10²³ atoms, which is the number of atoms in 12g of ¹²C.
Moles and Particles
- 1 mole = 6 × 10²³ atoms or molecules or ions
- Moles are represented in chemical formulas, e.g., H₂ + Br₂ → 2HBr (2 moles, 1 mole, 1 mole)
Converting Moles to Grams
- Moles × Mᵣ (relative molecular mass) = Mass (in grams)
- Example: Calculate the mass of 0.33 moles of calcium chloride (CaCl₂) → Mᵣ = 111, Mass = 0.33 × 111 = 37g
Molar Volume of Gases
- Avogadro's Law: Equal volumes of gases, under the same conditions of temperature and pressure, contain equal numbers of molecules.
- At standard temperature and pressure (s.t.p.), 1 mole = 22.4L = 22,400cm³
- Example: Calculate the number of moles in 560 cm³ of N₂ at s.t.p. → 0.025 moles
Calculations Involving Moles
- (a) Moles → atoms/molecules: 0.75 moles of Na = 4.5 × 10²³ atoms
- (b) Grams → atoms/molecules: 950g carbon dioxide balloon → 21.59 moles → 1.295 × 10²⁵ molecules
- (c) Atoms/molecules → moles: 4.5 × 10²² atoms of Copper → 0.075 moles
- (d) Atoms/molecules → moles: 6× 10²² molecules of ethane → 0.1 moles → 2.8g
- (e) Volumes → atoms/molecules: 500 cm³ of SO₂ at s.t.p. → 0.02232 moles → 4.017 × 10²² atoms
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Description
Understand Avogadro's Law, mole concept, and its applications in chemistry. Learn how to calculate moles, mass, and volume of substances.
