Chemical changes

• What are the terms used to describe the strength and concentration of acids?

  'Dilute and concentrated', and 'weak and strong'
• How does the concentration of hydrogen ions in a solution affect pH?

  It affects the numerical value of pH, with higher concentrations resulting in lower pH values.
• What is the difference between ethanoic acid and hydrochloric acid?

  • Ethanoic acid is a weak acid.
  • Hydrochloric acid is a strong acid.
• Why is it important to use the same concentrations of each acid in the experiment?

  To ensure a fair comparison of their properties.
• What is the concentration of hydrochloric acid that requires labeling as corrosive?

  1. 0 mol/dm³
• What happens to the labeling of hydrochloric acid when it is diluted to 0.10 mol/dm³?

  It only requires labeling as irritant.
• What are examples of strong acids?

  Hydrochloric acid, sulfuric acid, and nitric acid.
• What are examples of weak acids?

  Ethanoic acid, citric acid, and carbonic acid.
• Why do acids need to dissolve in water to show their acidic properties?

  Because all acids ionise in water to form H$^+$$(aq)$ ions and negative ions.
• How do strong acids ionise in water?

  All the molecules ionise completely.
• How do weak acids behave in water compared to strong acids?

  Most molecules stay intact and do not release H$^+$ ions into the solution.
• What is the equilibrium position in weak acids?


  It is reached when both whole molecules and their ions are present.
• How does the concentration of H$^+$$(aq)$ ions compare between strong and weak acids of equal concentration?


  The strong acid will have a higher concentration of H$^+$$(aq)$ ions.
• What is the pH of a 0.10 mol/dm³ solution of dilute hydrochloric acid?


  1. 0
• What happens to the pH value when the concentration of hydrochloric acid is diluted ten times?

  The pH value increases to 2.0.
• How does the pH change with further dilution to 0.0010 mol/dm³?

  The pH value becomes 3.0.
• What is the relationship between the concentration of H$^+$$(aq)$ ions and pH values?


  • As the concentration of H$^+$$(aq)$ ions decreases by a factor of 10, the pH value increases by one unit.
  • Increasing the concentration of H$^+$$(aq)$ ions by a factor of 10 decreases the pH by one unit.
• What is the pH value of pure water?

  7
• What distinguishes alkalis from other bases?

  Alkalis are soluble bases that dissolve in water.
• What ions do all acids produce in aqueous solution?

  H$^+$$(aq)$ ions.
• What is the role of indicators in measuring pH?

  Indicators change color when added to acids and alkalis.
• What does the pH scale indicate?

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

  0 to 14
• What is the pH of a neutral solution?

  7
• How can you measure pH accurately?

  Using a pH meter or pH sensor.
• What happens when an acid reacts with an alkali?

  • A neutralisation reaction occurs.
  • Example: Hydrochloric acid reacts with sodium hydroxide to form sodium chloride and water.
• What is produced when potassium hydroxide dissolves in water?

  Potassium ions (K$^+$$(aq)$) and hydroxide ions (OH$^-(aq)$).
• What is produced when hydrobromic acid dissolves in water?


  H$^+$$(aq)$ ions and Br$^-(aq)$ ions.
• What are the advantages and disadvantages of using universal indicator paper versus a pH sensor?

  Advantages of universal indicator:

  • Simple to use.
  • Inexpensive.

  
  

  Disadvantages of universal indicator:

  • Less accurate than a pH sensor.
  • Limited color range.

  
  

  Advantages of pH sensor:

  • Provides precise measurements.
  • Can be connected to data-loggers.

  
  

  Disadvantages of pH sensor:

  • More expensive.
  • Requires calibration.
• What happens to the pH when a strong acid is added slowly to a strong alkali?

  The pH decreases as the acid neutralizes the alkali.
• What is the general reaction when an acid reacts with a carbonate?

  Acid + carbonate → salt + water + carbon dioxide.
• What is produced when hydrochloric acid reacts with sodium hydroxide?

  Sodium chloride and water.
• What is the role of sodium hydroxide in neutralization reactions?

  Sodium hydroxide acts as a base to neutralize acids.
• What is the significance of the pH scale in chemistry?

  The pH scale helps to classify solutions as acidic, neutral, or alkaline.
• How does the concentration of hydrogen ions relate to the acidity of a solution?

  A higher concentration of hydrogen ions indicates a more acidic solution.
• What is the effect of dilution on the pH of a strong acid?

  Dilution increases the pH value of the acid.
• What is the relationship between pH and the strength of an acid?

  Stronger acids have lower pH values compared to weaker acids at the same concentration.
• Why is it important to wear eye protection during acid experiments?

  To prevent injury from splashes of corrosive substances.
• What is the significance of the equilibrium position in weak acids?

  It indicates the balance between ionized and non-ionized molecules in solution.
• How does the ionization of weak acids differ from that of strong acids?

  Weak acids do not ionize completely, while strong acids do.