Unit 1 Chemistry: Acids, Bases, Salts

• Which fruits contain citric acid and ascorbic acid?

  Strawberries and blueberries
• What is an indicator?

  An indicator is a substance that changes color in acid and a different color in alkali

  
• What is the name of the blue dye used as an indicator in 1300 AD?

  Litmus
• What color does red litmus paper turn in an alkaline solution?

  Blue
• What are the colors of phenolphthalein and methyl orange in acidic, alkaline, and neutral solutions?

  Phenolphthalein:

  • Acidic: colorless
  • Neutral: colorless
  • Alkaline: pink

  
  

  Methyl orange:

  • Acidic: red
  • Neutral: orange
  • Alkaline: yellow
• What is the definition of an acid?

  An acid is a substance that dissolves in water producing hydrogen ions (H+(aq))
• What is the definition of an alkali?

  An alkali is a substance that dissolves in water producing hydroxide ions (OH-(aq))
• What happens when ammonia (NH3) reacts with water?

  It produces hydroxide ions, making it an alkali
• What is the formula of hydrochloric acid?

  HCl
• How do strong acids differ from weak acids?

  Strong acids are completely ionised in water, while weak acids are partially ionised

  
• What is the ionisation equation for hydrochloric acid?

  HCl(aq) → H+(aq) + Cl-(aq)
• What is the ionisation equation for sulfuric acid?

  H2SO4(aq) → 2H+(aq) + SO4^2-(aq)
• What is the difference in ionisation between a strong acid and a weak acid?

  A strong acid fully ionises in water, while a weak acid only partially ionises

  
• What is the formula for ethanoic acid?

  CH3COOH
• What is the pH range for strong alkalis?

  12-14
• What does pH stand for?

  Power of hydrogen
• What is the pH of a neutral solution?

  pH 7
• What are the steps to determine the pH using universal indicator paper?

  1. Dip pH paper into the solution or add 3 drops of universal indicator to the solution
  2. Compare the color with the pH color chart
• What is the pH range for weak acids?

  Typically below 7
• What is the significance of a pH meter?

  A pH meter provides an accurate pH reading to at least one decimal place
• What is the difference between dilute and concentrated acids?

  A concentrated acid contains a large number of acid particles per unit volume, while a dilute acid contains a small number
• How do you determine which solution is more concentrated between 1.0 mol/dm³ ethanoic acid and 0.5 mol/dm³ nitric acid?

  The 1.0 mol/dm³ ethanoic acid is more concentrated
• What is the relationship between pH and the concentration of hydrogen ions in an acidic solution?

  The higher the concentration of hydrogen ions, the lower the pH
• What is the hazard symbol for corrosive substances?

  A symbol indicating burns and destroys living tissue
• What does the hazard symbol for explosive substances indicate?

  It indicates that the substance explodes if exposed to flame, heat, or is knocked
• What is the meaning of the hazard symbol for flammable substances?

  It indicates that the substance catches fire easily when in contact with air
• What does the hazard symbol for toxic substances indicate?

  It indicates that the substance can kill by poisoning
• What happens to the pH as the concentration of hydrogen ions increases?

  The lower the pH
• How is concentration measured in solutions?

  In moles per cubic decimetre of solution (mol/dm³)
• What is the volume of one cubic decimetre in cubic centimetres?

  1000 cm³
• What is the concentration of the acid HA mentioned in the study material?

  0.2 mol/dm³
• Why does a 1.0 mol/dm³ solution of HA have a lower pH than a 0.2 mol/dm³ solution?

  Because 1.0 mol/dm³ is a higher concentration
• What is the importance of safety in the laboratory?

  • All risks must be considered
  • Chemicals must be labelled with hazard symbols
  • An international system of labelling is used
  • Hazard symbols are recognized worldwide
• What does the hazard symbol for corrosive substances indicate?

  Burns and destroys living tissue
• What does the hazard symbol for explosive substances indicate?

  Explodes if exposed to flame, heat, or knocked
• What does the hazard symbol for flammable substances indicate?

  Catches fire easily when in contact with air
• What does the hazard symbol for toxic substances indicate?

  Can kill by poisoning
• What is the difference between a concentrated alkali and a dilute solution of an alkali?

  A concentrated alkali has a higher concentration of hydroxide ions
• What does it mean for sulfuric acid to be a strong acid?

  It completely dissociates in solution
• What does it mean for citric acid to be a weak acid?

  It partially dissociates in solution