amount of substance

• What is the definition of relative atomic mass (Ar)?


  The mean mass of an atom of an element, divided by one twelfth of the mean mass of an atom of the carbon-12 isotope.
• What is the definition of relative molecular mass (Mr)?


  The mean mass of a molecule of a compound, divided by one twelfth of the mean mass of an atom of the carbon-12 isotope.
• What is the term used for relative molecular mass in ionic compounds?


  Relative formula mass.
• What is the mole a unit of measurement for?


  Substances.
• What does the Avogadro Constant (L) represent?


  The number of particles in one mole of a substance.
• How can the number of particles in a sample of a substance be found?


  By using the Avogadro Constant (L) and the mass of the substance.
• What is the formula for calculating concentration in moles?


  Concentration = n / V
• What happens to gases and volatile liquids under standard conditions?


  They follow certain trends regarding pressure, volume, and temperature.
• What is the relationship between pressure and temperature for gases?


  Pressure is proportional to temperature.
• What is the ideal gas equation?


  PV = nRT
• What are the standard units for pressure, volume, and temperature in the ideal gas equation?

  Pressure in Pascals, volume in m³, temperature in Kelvin.
• What is the value of the ideal gas constant (R)?


  1. 31 JK⁻¹mol⁻¹.
• What is an empirical formula?


  The simplest whole number ratio of atoms of each element in a compound.
• How is the molecular formula determined from the empirical formula?


  Using the Mr of the empirical formula and the true Mr of the molecule to find a multiplier.
• Why must chemical equations be balanced before calculations?


  To ensure the reacting ratios are correct.
• What can balanced chemical equations be used to calculate?


  Reacting masses, percentage yield, and atom economy.
• What does a high atom economy indicate in industrial chemical processes?


  There is little or no waste product, making the process economically viable.
• Why is high atom economy beneficial for the environment?


  It uses less natural resources and often requires less energy.