mole concept

• mole is the amount of substance that contains as many elementary entities (atoms or molecules) as there are atoms in exactly 12 g of carbon-12.
• no of moles = mass in (g) / molar mass in (g/mol)
• The relative atomic mass (Ar) of an element is the average mass of one atom of that element relative to 1/12 the mass of an atom of carbon-12
• always take the big no for relative atomic mass
• relative molecular mass = avg mass of one molecule of an element or compound/ 1/12 mass of an atom of carbon-12
• Calculate the Mr of chlorine (35.5)

  2 × 35.5 = 71