The Mole

• What is the unit used to measure the amount of a substance?

  Mole
• What symbol is used to represent moles?


  n
• How is one mole defined in relation to the Avogadro constant?

  One mole is equivalent to the Avogadro constant
• What does the Avogadro constant represent?

  Number of particles in one mole of substance
• What is the value of the Avogadro constant?

  6.02 × 10²³
• What is the molar mass (M_r) of water (H₂O)?

  18
• How many particles are in one mole of water?

  6.02 × 10²³ particles
• What is the mass of one mole of water?

  18 g
• How many particles are in one mole of chlorine (Cl) atoms?

  6.02 × 10²³ particles
• Does the Avogadro constant change for different substances?

  No, it never changes
• How many atoms are in 0.4 moles of magnesium (Mg)?

  2.41 × 10²³ atoms
• How many moles are in 7.83 × 10²³ atoms of strontium (Sr)?

  13 moles
• What is the relationship between mass, moles, and molar mass?

  • One mole has a mass in grams equal to its M_r
  • Formula triangle: n = m / M
• What is the molar mass (M_r) of iron oxide (Fe₂O₃)?

  160
• How many moles are in 5000 g of silver (Ag) with an A_r of 108?

  46.3 moles
• What is the mass of 6 moles of pyrite (FeS₂) with an M_r of 120?

  720 grams
• What is concentration in chemistry?

  • Amount of solute in a solvent
  • Measured in moles per dm³
• What is the formula for calculating concentration?

  Concentration = moles ÷ volume
• What is the concentration of 0.5 moles of solute in 250 cm³ of solution?

  2 mol/dm³
• How to calculate concentration in grams/dm³?

  • Divide mass of chemical by volume of solvent
  • Example: 5 g of KCl in 0.1 dm³ gives 5 g/dm³
• What is the concentration in grams/dm³ of a 0.2 mol/dm³ solution of hydrochloric acid (HCl) with M_r of 36.5?


  7.3 grams/dm³
• What is the ideal gas equation?

  • pV = nRT
  • p = pressure (Pa)
  • V = volume (m³)
  • n = number of moles
  • R = gas constant (8.31 J/K/mol)
  • T = temperature (K)
• What does the kinetic theory of gases state?

  Gases are constantly moving in random directions
• What is the standard temperature and pressure (STP) for gases?

  0°C and 101,325 Pa
• How to calculate the volume of gaseous water vapor in a cloud with given pressure, moles, and temperature?

  Use V = nRT ÷ p
• What is the volume of water vapor at 200,000 Pa, 1.71 moles, and 18°C?

  20.1 dm³
• How to calculate the number of moles of gas in a closed flask with known mass, pressure, and temperature?

  Use n = pV ÷ RT
• What is the molar mass of a gas if 3.32 g is contained in 0.081 moles?

  40.97 g/mol
• What are the variables in the ideal gas equation?

  • p = pressure (Pa)
  • V = volume (m³)
  • n = number of moles
  • R = gas constant (8.31 J/K/mol)
  • T = temperature (K)