C3 - Quantitative Chemistry

• Percentage mass of an element in a compound =

  (Atomic mass x number of atoms in element) / R.Formula Mass
• What is avogadros constant?

  6.02 x 10^23
• The mass of 1 mole of an element = Relative atomic mass
• Number of moles = mass in grams of element/compound / Relative atomic/formula mass of element/compound
• The conservation of mass states that no atoms are lost or made during a reaction so the mass of products = mass of reactants
• If the mass of reactants increases, it is because one of the reactants is a gas found in the air which reacts to form part of the products
• If the mass of reactants decreases, it is because one of the products is a gas, if the vessel isn't closed then the gas can escape as it is formed
• number of moles = concentration x volume
• volume of gas = mass of gas / Mr of gas