Chemistry

• What does the conservation of mass state during a chemical reaction?


  No atoms are lost or made during a chemical reaction.
• What is relative atomic mass (A)?


  The relative mass of one atom of a substance.
• What does the relative formula mass (Mr) represent?


  The number on the periodic table of the element.
• What is a mole (mol)?


  The number of atoms in the formula.
• What is Avogadro's constant (N)?


  N = 6.02 x 10²³ particles in one mole of substance.
• How is the mass of one mole (g) related to relative formula mass?


  It is numerically the same as the relative formula mass.
• What is a limiting reactant?


  The reactant that is completely used up in a chemical reaction.
• What does atom economy measure?


  A measure of the percent of starting materials that end up in useful products.
• Why might the mass appear to increase during a reaction?

  If one of the reactants is a gas that combines with a solid or liquid.
• What is the equation to calculate moles?


  Moles = mass/Mr
• How do you calculate moles from concentration and volume?


  Moles = concentration (mol/dm³) x volume (dm³)
• What is the formula for percent yield?


  % yield = (actual mass / expected mass) x 100
• How do you calculate gas volume in dm³?


  Gas volume (dm³) = number of moles x 24
• What are the steps to calculate unknown mass or concentration?

  1. Work out moles of known substance using mol/Mr, or n = c x v
  2. Use the equation ratio to find moles of the unknown substance
  3. Calculate mass or concentration of the unknown using n = m/Mr, or n = c x v
• Why might the mass appear to decrease during a reaction?


  If one of the products is a gas that escapes into the atmosphere.
• What is the result of a flame test for sodium ions?


  Orange flame.
• What color flame indicates potassium ions?


  Lilac flame.
• What color flame is produced by calcium ions?


  Brick red flame.
• What color flame indicates copper ions?

  Green flame.
• What color flame is produced by magnesium ions?


  Cream and a blue flame.
• What is the result of adding sodium hydroxide to a solution containing Iron (II) ions?


  Green precipitate.
• What is the result of adding sodium hydroxide to a solution containing Iron (III) ions?


  Brown precipitate.
• What is the result of adding sodium hydroxide to a solution containing Copper (II) ions?


  Blue precipitate.
• What is the result of adding sodium hydroxide to a solution containing Aluminium ions?


  White precipitate.
• What is the result of adding sodium hydroxide to a solution containing Magnesium ions?


  White precipitate.
• What is the result of adding dilute nitric acid and then silver nitrate to a solution containing Chloride ions?


  White precipitate.
• What is the result of adding dilute nitric acid and then silver nitrate to a solution containing Bromide ions?


  Cream precipitate.
• What is the result of adding dilute nitric acid and then silver nitrate to a solution containing Iodide ions?


  Yellow precipitate.
• What happens when dilute acid is added to a solution containing Carbonate ions?


  Carbon dioxide gas makes limewater milky.
• What is the result of adding dilute hydrochloric acid and barium chloride to a solution containing Sulfate ions?


  White precipitate forms.
• What is the test for oxygen gas?


  It relights a glowing splint.
• What is the test for hydrogen gas?


  It ignites and makes a popping noise.
• What is the test for chlorine gas?


  It bleaches damp blue litmus paper.
• What is the test for carbon dioxide gas?


  It turns limewater (calcium hydroxide solution) cloudy.
• What is a pure substance?


  Made up of one component or compound.
• What is the melting point?


  A solid goes liquid at a specific temperature.
• What is the boiling point?


  A liquid boils at a specific temperature.
• What is chromatography and its components?


  • Chromatography is a technique used to separate components in a mixture.
  • Components are kept moving in a defined direction.
  • Involves stationary phase (e.g., silica) and mobile phase (the solvent).
• What is the Rf value in chromatography?


  Distance travelled by substance / Distance travelled by solvent.
• What are the advantages and applications of chromatography?


  Advantages:

  • Quicker
  • More accurate
  • More sensitive

  
  

  Applications:

  • Identifies metal ions present
  • Measures their concentrations