• The?Avogadro constant?(N_A?or?L) is the number of particles equivalent to the relative?atomic?mass?or?molecular mass?of a substance
  • The Avogadro constant applies to atoms, molecules, ions and electrons

   

• The value of?N_A?is?6.02 x 10²³?g mol^-1
• The mass of a substance with this number of particles is called a?mole?(mol)
  • The?mass?of a substance containing the same number of fundamental units as there are atoms in exactly 12.00 g of?¹²C

   

• One mole of any element is equal to the relative atomic mass of that element in grams
  • If you had one mole of carbon in your hand, that is 6.02 x 10²³?atoms of carbon, you would have a mass of 12.00 g
  • One mole of water would have a mass of (2 x 1 + 16) = 18 g

   

Answer 1:

• • The relative atomic mass of Na is 22.99
  • Therefore, 1 mol of Na has a mass of 22.99 g mol^-1
  • 1 mol of Na will contain 6.02 x 10^23?atoms of Na (Avogadro’s constant)

   

Answer 2

• • The relative atomic mass of H is 1.005
  • Since there are 2 H atoms in H₂, the mass of 1 mol of H₂?is (2 x 1.005) 2.01 g mol^-1
  • 1 mol of H₂?will contain 6.02 x 10^23?molecules of H₂
  • Since there are 2 H atoms in H₂, 1 mol of H₂?will contain 1.204 x 10^24?H atoms

Answer 3

• • The relative atomic mass of Na and Cl is 22.99 and 35.45 respectively
  • Therefore, 1 mol of NaCl has a mass of (22.99 + 35.45) 58.44 g mol^-1
  • 1 mol of NaCl will contain 6.02 x 10^23?formula units of NaCl
  • Since there are Na and Cl ions in NaCl, 1 mol of NaCl will contain 1.204 x 10^24??ions in total