4.1 Acids & Bases

• What does the pH scale measure?

  The pH scale measures how acidic or alkaline a solution is.
• What is the range of the pH scale?

  The pH scale ranges from 0 to 14.
• What pH value indicates a neutral solution?

  A neutral solution has a pH of 7.
• What is the pH of stomach acid?

  The pH of stomach acid is around 2.
• What is the pH of acid rain?

  The pH of acid rain is around 4.
• What is the pH of washing up liquid?

  The pH of washing up liquid is around 9.
• What is the pH of bleach?

  The pH of bleach is around 12.
• What are indicators used for in measuring pH?

  Indicators are used to change color depending on the pH of a solution.
• What is a wide range indicator?

  A wide range indicator changes color across a wide range of pH values.
• What is the most common example of a wide range indicator?

  The most common example of a wide range indicator is universal indicator.
• What colors does the universal indicator show at different pH levels?

  Universal indicator shows deep red at low pH and bluey purple at high pH.
• How does a pH probe measure pH?

  A pH probe measures pH by dipping it into a solution and getting a numerical reading.
• Why is a pH probe more accurate than an indicator?

  A pH probe is more accurate because it removes human judgment in color interpretation.
• How is an acid defined in terms of pH?

  An acid is defined as a substance that forms aqueous solutions with a pH of less than 7.
• What do acids release in water?

  Acids release hydrogen ions in water.
• How is a base defined in terms of pH?

  A base is defined as any substance with a pH greater than 7.
• What is an alkali?

  An alkali is a base that dissolves in water to form a solution with a pH greater than 7.
• What ions do alkalis form in water?

  Alkalis form hydroxide ions (OH^-) in water.
• What is produced in a neutralization reaction between an acid and a base?

  A neutralization reaction produces a salt and water.
• What is the reaction between hydrochloric acid and sodium hydroxide?

  Hydrochloric acid reacts with sodium hydroxide to form sodium chloride and water.
• How can neutralization reactions be represented in terms of ions?

  Neutralization reactions can be represented by H⁺ from the acid and OH^- from the base forming H₂O.
• What is the pH of the products in a neutralization reaction?

  The pH of the products in a neutralization reaction should be 7, indicating neutrality.
• What are some common acids mentioned in the material?

  Common acids include hydrochloric acid, sulfuric acid, and nitric acid.
• What are some common bases mentioned in the material?

  Common bases include sodium hydroxide and calcium carbonate.
• What are the key characteristics of acids and bases?

  • Acids: pH less than 7, release H⁺ ions in water.
  • Bases: pH greater than 7, release OH^- ions in water.
  • Alkalis: A subgroup of bases that are soluble in water.
• What are the steps in a neutralization reaction?

  1. Acid and base react.
  2. H⁺ ions from the acid combine with OH^- ions from the base.
  3. Produce water (H₂O) and a salt.
  4. Resulting pH is 7 (neutral).
• What are some examples of common acids and bases?

  • Common Acids: Hydrochloric acid, sulfuric acid, nitric acid.
  • Common Bases: Sodium hydroxide, calcium carbonate.