Acids and alkalis

• What is the pH scale used to measure?

  The acidity or alkalinity of a solution
• What does a low pH value indicate?

  A solution is more acidic
• What is the pH of pure water?

  7
• What is the pH of stomach acid?

  Approximately 2
• What is the pH of acid rain?

  Approximately 4
• What is the pH of washing up liquid?

  Approximately 9
• What is the pH of bleach?

  Approximately 12
• What is an indicator in the context of pH measurement?

  A chemical dye that changes color depending on the pH
• What is a wide range indicator?

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

  Universal indicator
• What colors does the universal indicator show at low and high pH?

  Deep red at low pH and bluey purple at high pH
• How does a pH probe measure pH?

  By dipping the probe into a solution and electronically measuring the pH
• Why is a pH probe more reliable than an indicator?

  It removes the need for human judgment in color interpretation
• How is an acid defined in terms of pH?

  Any substance that forms aqueous solutions with a pH of less than 7
• What do acids release in water?

  Hydrogen ions
• How is a base defined in terms of pH?

  Any substance with a pH greater than 7
• What is an alkali?

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

  Hydroxide ions (OH^-)
• What is produced in a neutralization reaction between an acid and a base?

  A salt and water
• What is the reaction between hydrochloric acid and sodium hydroxide?

  Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water
• How can neutralization reactions be represented in terms of ions?

  H⁺ from the acid and OH^- from the base combine to form H₂O
• What is the pH of the products in a neutralization reaction?

  7, because they are neutral
• What are some common acids and bases encountered in chemistry?

  Common acids:

  • Hydrochloric acid
  • Sulfuric acid
  • Nitric acid

  
  

  Common bases:

  • Sodium hydroxide
  • Calcium carbonate
• Why is it useful to learn about common acids and bases?

  They frequently appear in chemistry contexts