Chem

• What is the mass number composed of?

  Number of protons and neutrons
• What gas is a compound?

  Carbon dioxide
• What is the most abundant gas in the atmosphere?

  Nitrogen
• What is the least reactive gas?

  Argon
• What gas is formed by complete combustion of carbon dioxide?

  Lighted splint produces squeaky pop
• What are the observations when sodium reacts with water?

  • Sodium moves on the surface
  • Effervescence occurs
  • Indicator turns pink
  • Sodium gets smaller
  • Sodium melts into a ball
• Why is potassium more reactive than sodium?

  Potassium has a different electron configuration
• What is the electron configuration of sodium?

  2, 8, 1
• What is the electron configuration of potassium?

  2, 8, 8, 1
• Why is aluminium malleable?

  Layers can slide over each other
• How does aluminium conduct electricity?

  Delocalised electrons can move
• Is aluminium more or less reactive than carbon?

  More reactive
• How does aluminium form at the negative electrode?

  Aluminium ions are attracted to the negative electrode
• Why is carbon dioxide gas produced at the electrode?

  Electrodes react with oxygen
• How to prepare a dry sample of silver chloride from copper II chloride solutions?

  1. Mix silver nitrate and copper II chloride
  2. Filter the silver chloride
  3. Wash with distilled water
  4. Dry in warm oven or on windowsill
• What causes an anomalous result in experiments?

  Tube was on a slant
• How is crude oil separated?

  Crude oil is heated
• What happens to gases in the separation of crude oil?

  Gases rise up the column
• How does the temperature vary in the crude oil separation column?

  Hotter at the bottom, colder at the top
• What happens to vapours in the crude oil separation process?

  Vapours condense at their boiling points
• What are the conditions for cracking crude oil?

  Temperature of 600℃ - 700℃
• What catalyst is used in cracking?

  Catalyst of silica
• How do oxides of nitrogen form in car engines?

  Nitrogen reacts with oxygen at high temperature
• What color flame does Li⁺ produce?

  Red flame
• What color flame does Na⁺ produce?

  Yellow flame
• What color flame does K⁺ produce?

  Lilac flame
• What color flame does Ca²⁺ produce?

  Orange-red flame
• What color flame does Cu²⁺ produce?

  Blue-green flame
• What test produces a squeaky pop?

  Hydrogen test
• What happens to a glowing splint in oxygen?

  It relights
• What happens to lime water when carbon dioxide is present?

  Lime water goes cloudy
• What happens to damp red litmus paper in ammonia?

  It turns blue
• What happens to litmus paper in chlorine?

  It bleaches to white
• What color precipitate does Copper II produce?

  Blue precipitate
• What color precipitate does Iron II produce?

  Green precipitate
• What color precipitate does Iron III produce?

  Brown precipitate