What is the mole? Study design the mole concept; Avogadro constant; determination of the number of moles of atoms in a sample of known mass; calculation of the molar mass of ionic compounds

the mole concept; Avogadro constant; determination of the number of moles of atoms in a sample of known mass; calculation of the molar mass of ionic compounds The mole (n) Atoms are extremely tiny, so chemists never deal with them one at a time. The mole is the amount of substance that contains as many particles (atoms, ions or molecules) as there are atoms in exactly 12g of the carbon-12 isotope. The number of atoms has been experimentally estimated to be 6.02 x 1023 (Avogadro’s constant). To find the mass of one mole of an element add “g” to the relative atomic mass of that element.

Converting number of particles to number of moles and vice versa Number of moles (n)= Number of particles (N) Avogadro’s constant (NA) Number of particles(N)=number of moles(n)x Avogadro’s(NA) N n NA

the mole concept; Avogadro constant; determination of the number of moles of atoms in a sample of known mass; calculation of the molar mass of ionic compounds What is the mole? A mole is the amount of a substance of a system which contains as many elementary particles as there are Carbon atoms in 12 grams of 12C STANDARD: 12 grams of 12C One Mole of 12C MICROSCOPIC LEVEL: Number of particles X of 12C atoms X=6.02 x 10 23=Avogadro’s number MACROSCOPIC LEVEL: Mass 12 grams

the mole concept; Avogadro constant; determination of the number of moles of atoms in a sample of known mass; calculation of the molar mass of ionic compounds WHY 12C and 12 g? As long as they have the same number of atoms, the mass ratios between elements do not change. Therefore, we can count the number of particles by weighing. ATOMIC LEVEL MACROSCOPIC LEVEL Relative Atomic/Molecular Mass Molar mass (a mass per mole) Proportional relationships relative to C-12 C 12 O 16 H 1 N 14 C 12 g O 16 g H 1 g N 14 g 1 mole = the number of 12C atoms in 12 g of 12C

Relative Atomic Mass / Molecular Mass Molar Mass ( a mass per mole) 1 MOLE C 12 g O 16g C 12 O 16 1 MOLE

Then... 12g of C has the same number of atoms as 14g of N. 24g of C has the same number of atoms as 28g of N. 32g of O has twice the number of particles than 12g of C.

the mole concept; Avogadro constant; determination of the number of moles of atoms in a sample of known mass; calculation of the molar mass of ionic compounds Molar mass (M) note that the little “r” is gone because now we are talking about mass. The mass of 1 mole of the element. The unit is grams per mole (g/mol) Molar mass of carbon atoms = mass of 1 mol of C atoms = 12 g/mol 12g of carbon contains 6.02 x 1023 atoms of carbon Can be worked out by calculating the relative molecular mass (Mr) of a substance and use the unit g/mol.

Molar mass (M) Molecular compounds: Numerically equal to the relative molecular mass (Mr ) expressed in grams per mole Molar mass of water molecules = mass of 1 mol of H2O molecules = 18 g/mol 18g of water contains 6.02 x 1023 molecules of water

Molar mass (M) Ionic compounds: the mole concept; Avogadro constant; determination of the number of moles of atoms in a sample of known mass; calculation of the molar mass of ionic compounds Molar mass (M) Ionic compounds: The relative formula mass is found by adding together the relative atomic mass of each atom in the formula of the compound Mr of CuSO4 = Ar (Cu)+ Ar (S)+ 4x Ar (O) = 63.5+32.1+4x16 = molar mass 159.6 g/mol

Converting mass to number of moles and vice versa Number of moles (n) = Mass (m in g) Molar mass (M in g/mol) Mass(m in g)=Number of moles(n)xMolar mass(M in g/mol) m n M