Quantitative Chemistry

• What is the conservation of mass?

  In a chemical reaction, the total mass of the products is equal to the total mass of the reactants
• Why must a symbol equation balance?

  Because no atoms are lost or made
• What are half equations used for?

  To show what happens to one reactant in a chemical equation.
• What are ionic equations used for?

  To show the different species that are involved in an equation.
• What does the term species mean in Chemistry?

  The different atoms, molecules or ions that are involved in a reaction.
• What are spectator ions?

  Ions that are present during the reaction but are left unchanged
• What is the relative formula mass of a compound?

  The sum of all the relative atomic masses of all the atoms in the formula
• Why does the mass of magnesium increase when burned in air?

  Because the magnesium reacts with the oxygen to form magnesium oxide, and oxygen has mass
• Why does the mass of calcium carbonate decrease when heated?

  Because calcium carbonate decomposes to form calcium oxide and carbon dioxide. Because one of the products is a gas, the gas is able to escape into the air
• What is a mole?

  The number of particles (atoms, ions or molecules) contained in a substance
• What is the Avogadro constant?

  One mole of any substance contains the same number of particles - 6.02 x 10 (to the power of 23)
• How can you calculate the amount of substance in a given mass of substance?

  Mass ÷ atomic mass
• What is the concentration of a solution?

  Amount of substance ÷ volume
• What is the volume of 1 mole of any gas?

  Amount x 24dm (cubed)
• What is titration?

  An accurate technique used to find out how much of an acid is needed to neutralise an alkali
• What must you use in titrations?

  A suitable indicator
• How do you calculate the percentage yield?

  yield from reaction ÷ maximum theoretical yield x 100
• What is the atom economy?

  The amount of reactant that is turned into useful product
• Why might scientist choose reaction pathways that have a high atom economy?

  For economic reasons and sustainable development as more products are made and less waste is produced.
• What are the 2 ways that ethanol can be produced?

  Fermentation and Hydration
• What is an addition reaction?

  All the reactant atoms end up in the desired product
• How is ethanol formed through hydration?

  Ethene is reacted with steam (H20) to form ethanol
• What is the equation for atom economy?

  Relative formula mass ÷ sum of the relative formula mass of all products / reactants x 100