pH scales and indicators

• What is the purpose of indicators in chemistry?

  Indicators classify chemicals as acidic, neutral, or alkaline.
• How is the pH scale used in chemistry?

  The pH scale measures the acidity and alkalinity of solutions.
• What happens when an acid is neutralized?

  It forms a salt.
• What is the pH value of a neutral solution?

  A neutral solution has a pH value of 7.
• What causes acidity in a solution?

  Acidity is caused by a high concentration of hydrogen ions.
• What is a base in chemistry?

  A base is a substance that reacts with an acid to neutralize it and produce a salt.
• What is an alkali?

  An alkali is a base that is soluble in water.
• What is the pH range for acidic solutions?

  Acidic solutions have a pH value below 7.
• What is the pH range for alkaline solutions?

  Alkaline solutions have a pH value above 7.
• What happens to universal indicator when added to a solution?

  It changes color to show the pH of the solution.
• How can a more accurate pH value be obtained?

  A more accurate value can be obtained using a pH probe.
• What are the three categories of solutions based on pH?

  • Acidic: pH < 7
  • Neutral: pH = 7
  • Alkaline: pH > 7
• What are the characteristics of pure water in terms of pH?

  • Pure water is neutral.
  • It has a pH value of 7.
• What is the most commonly used indicator in laboratories?

  Universal indicator is the most commonly used indicator.
• What is the role of hydrogen ions in determining acidity?

  • High concentration of hydrogen ions leads to acidity.
  • Low concentration of hydrogen ions leads to neutrality or alkalinity.
• What is the significance of the pH scale in chemistry?

  • Measures acidity and alkalinity.
  • Helps classify substances as acidic, neutral, or alkaline.
• The pH scale

  
• What is the purpose of the pH scale?

  To measure acidity and alkalinity
• What happens when an acid is neutralised?

  It forms a salt
• What are the classifications of chemicals based on pH?

  • Acidic
  • Neutral
  • Alkaline
• What is produced when acids dissolve in water?

  Hydrogen ions, H+
• Why are hydrogen ions sometimes called protons?

  Because hydrogen ions are the same as a hydrogen nucleus
• What is the equation for hydrochloric acid dissolving in water?

  HCl(aq) → H+(aq) + Cl-(aq)
• What do alkalis produce when they dissolve in water?

  Hydroxide ions, OH^-
• What is the equation for sodium hydroxide dissolving in water?

  NaOH(aq) → Na⁺(aq) + OH^-(aq)
• How does ammonia behave in solution?

  It produces NH₄⁺ and OH^- ions
• What is a base in relation to an acid?

  A base is chemically opposite to an acid
• What occurs during a neutralisation reaction?

  H⁺ ions react with OH^- ions to form water
• What is the equation for the neutralisation reaction?

  H⁺(aq) + OH^-(aq) → H₂O(l)
• What do hydrochloric acid and sodium hydroxide produce when they react?

  Water and sodium chloride solution
• What is sometimes referred to as 'proton transfer'?

  The process of neutralisation reactions
• What are the key components of a neutralisation reaction?

  • H⁺ ions from acids
  • OH^- ions from alkalis
  • Formation of water
  • Formation of a salt
• What ions are involved in the neutralisation of hydrochloric acid and sodium hydroxide?

  H+ ions and OH- ions
• What is the pH scale used for?

  To measure acidity and alkalinity
• What happens when an acid is neutralised?

  It forms a salt
• What distinguishes strong acids from weak acids?

  • Strong acids dissociate fully in water to produce H⁺ ions.
  • Weak acids do not fully dissociate; only a small percentage forms H⁺ ions.
• How many moles of H$^+$ ions are produced from one mole of hydrochloric acid (HCl)?


  One mole of H$^+$ ions
• Why do strong acids have lower pH values than weak acids?

  Because strong acids dissociate fully, producing more H$^+$ ions
• What is the effect of strong acids on the rate of reaction compared to weak acids?

  Strong acids react faster with substances than weak acids
• What is the temperature rise during a reaction with strong acids compared to weak acids?

  The temperature rise is higher with strong acids