Acidic and alkaline solutions

• What is the purpose of indicators in solutions?

  Indicators are used to determine whether a solution is acidic or alkaline.
• What happens when acids react with metals, bases, and carbonates?

  Acids react with these substances to produce salts.
• What is neutralisation in chemistry?

  Neutralisation is the reaction between an acid and a base.
• What defines an acid in terms of hydrogen ions?

  • An acid produces more hydrogen ions than hydroxide ions when dissolved in water.
  • Acids have a pH lower than 7.
• What is the chemical representation of hydrochloric acid in aqueous solution?

  HCl(aq) → H⁺(aq) + Cl^-(aq)
• What is the pH scale used for?

  • The pH scale measures the acidity or alkalinity of a solution.
  • A pH value below 7 indicates acidity, while above 7 indicates alkalinity.
• What defines an alkali in terms of hydroxide ions?

  • An alkali produces more hydroxide ions than hydrogen ions when dissolved in water.
  • Alkalis have a pH greater than 7.
• What is the chemical representation of sodium hydroxide in aqueous solution?

  NaOH(aq) → Na⁺(aq) + OH^-(aq)
• What is a neutral solution?

  • A neutral solution is neither acidic nor alkaline.
  • It has a pH value of 7.
• How can the pH of a solution be measured?

  The pH can be measured using a pH probe or estimated using universal indicator and a colour chart.
• What is universal indicator?

  • A chemical solution that produces many different colour changes corresponding to different pH levels.
  • It is used to determine the acidity or alkalinity of a solution.
• What does litmus paper indicate?

  • Red litmus paper stays red in acidic solutions and turns blue in alkaline solutions.
  • Blue litmus paper turns red in acidic solutions and stays blue in alkaline solutions.
• What happens to red litmus paper in an alkaline solution?

  Red litmus paper turns blue.
• What happens to blue litmus paper in an acidic solution?

  Blue litmus paper turns red.
• What are the differences in the behaviour of red and blue litmus paper in acidic and alkaline solutions?

  • Red litmus paper:
  • Stays red in acidic
  • Stays red in neutral
  • Turns blue in alkaline
  • Blue litmus paper:
  • Turns red in acidic
  • Stays blue in neutral
  • Stays blue in alkaline