2024

• What is the time span shown in Figure 1 for copper production?

  1900 to 2010
• What conclusion can be drawn about copper production between 1900 and 1925?

  It doesn't increase much
• What happens to copper production after 1925?

  It increases rapidly
• What is the difference between pure copper and the alloy of copper and zinc?

  • Pure copper has atoms of the same size.
  • Alloy has atoms of different sizes.
  • Alloy layers are distorted and harder.
• Why is the alloy of copper and zinc harder than pure copper?

  Atoms of different sizes distort layers
• What is the mass of the alloy sample mentioned?

  1. 25 g
• How much zinc is in the 5.25 g alloy sample?

  0.70875 g
• What is the mass of copper in the 5.25 g sample?

  1. 54 g
• What is the formula of the acid used to prepare copper sulfate?

  H₂SO₄
• Why is excess copper carbonate used in the reaction?

  To ensure all acid reacts
• How can copper sulfate crystals be produced from the solution?

  Heat and cool for 24 hours
• What happens to copper carbonate when it is thermally decomposed?

  It produces carbon dioxide gas
• Compare the structure and bonding of sodium chloride and oxygen.

  • Sodium chloride: Giant ionic lattice, ionic bonding.
  • Oxygen: Simple covalent molecule, shared electrons.
• What is meant by a 'strong acid'?

  Fully ionises or dissociates
• What does 'dilute aqueous solution' mean?

  Small number of H+ ions in large volume
• How does the hydrogen ion concentration change when pH changes from 1 to 3?

  Decreases by a factor of 100
• What is the ionic equation for the reaction between an acid and an alkali?

  H+ + OH- → H₂O
• What is the ratio of moles of magnesium carbonate to nitric acid in the reaction?

  1. 2
• What color does universal indicator turn when added to nitric acid?

  Red
• What are two improvements to the method for accurate results in the magnesium carbonate experiment?

  • Use a consistent time period for measurements.
  • Ensure thorough mixing of reactants.
• What is produced when nitrogen reacts with hydrogen?

  Ammonia (NH₃)
• How many electrons are shown in the dot and cross diagram for ammonia?

  Two on nitrogen, one each on hydrogen
• What is the mass of hydrogen needed to produce 25 g of ammonia?

  1. 41 g
• What is the bond energy of the H−H bond?

  498 kJ/mol
• What happens to the positive carbon electrodes during aluminium extraction?

  • React with oxygen.
  • Form carbon dioxide gas.
  • Need to be replaced.
• What is one metal found in the Earth as the metal itself?

  Gold
• What is the most economical method for extracting metal Z from its oxide?

  Reduction with carbon
• What is substance X used in the electrolysis cell for aluminium extraction?

  Cryolite
• What is the structure of carbon nanotubes?

  Hexagonal rings of carbon atoms
• What is one use of carbon nanotubes?

  Lubricant or drug delivery
• How many moles of carbon are in a nanotube with 2380 carbon atoms?

  $0.395 \text{ mol}$
• Why can carbon nanotubes conduct electricity?

  Delocalised electrons can carry charge