Draw one line from each water treatment step to its correct purpose.

• Step:

  • Filtration
  • Sedimentation

• Purpose:

  • Allow heavier suspended solids to settle to the bottom of a tank
  • Remove small insoluble particles like sand and silt by passing through gravel beds
  • Kill pathogenic microbes and bacteria
  • Neutralise dissolved acidic compounds

Which two of the following options are commonly used to sterilise fresh water to make it potable? Choose two options.

• Chlorine gas
• Argon gas
• Ultraviolet (UV) light
• Methane
• Sulfur dioxide

Which two methods can demonstrate the presence of dissolved solids in a sample of river water?

• Test if the boiling point of the water is significantly higher than $100^{\circ }C$ at standard pressure.
• Check if the liquid turns anhydrous copper(II) sulfate from white to blue.
• Evaporate all the liquid to see if a solid residue remains.
• Add a universal indicator solution to check if the pH is neutral.

Separate samples are tested to confirm the presence of the ions from the copper(II) chloride contaminant. Draw one line from each ion to the correct chemical reagent needed to identify it.

• Ion:

  • Copper(II) ion (${Cu}^{2+}$)
  • Chloride ion (${Cl}^{-}$)

• Reagent:

  • Dilute sulfuric acid
  • Barium chloride solution (acidified)
  • Sodium hydroxide solution
  • Silver nitrate solution (acidified)

How can pure water be produced from a sample of river water containing dissolved solids?

• Simple distillation
• Decanting
• Paper chromatography
• Gravity filtration