Acids & Bases

• Who is the presenter of the video on AQA acids and bases?

  Chris Harris
• What is the purpose of the video on AQA acids and bases?

  To provide a resource dedicated to AQA specifications for A-level chemistry students
• What types of resources are available alongside the video?

  • Whiteboard tutorials on specific chemistry topics
  • Exam paper walkthroughs to improve exam technique
  • A full range of revision videos for AQA
• What is the notation used to represent an acid in chemical reactions?

  HA
• What do Bronsted-Lowry acids do?

  They donate protons
• What do Bronsted-Lowry bases do?

  They accept protons
• What ions are formed when acids are mixed with water?

  Hydronium ions (H$_3$O$^+$)
• What is the simplified notation often used for hydronium ions?

  H$^+$
• What distinguishes strong acids from weak acids?

  • Strong acids dissociate almost completely in solution.
  • Weak acids dissociate poorly in solution.
• What is produced when bases react with water?

  Hydroxide ions (OH$^-$)
• What distinguishes strong bases from weak bases?

  • Strong bases dissociate almost completely in solution.
  • Weak bases dissociate poorly in solution.
• What is an example of a weak acid?

  Ethanoic acid
• What is an example of a strong acid?

  Hydrochloric acid
• What is an example of a strong base?

  Sodium hydroxide
• What is an example of a weak base?

  Ammonia (NH$_3$)
• What happens to the position of equilibrium when more acid is added to an acid-base reaction?

  • The equilibrium shifts to the right to produce more products.
• What happens to the position of equilibrium when more base is added to an acid-base reaction?

  • The equilibrium shifts to the right to produce more products.
• How does water behave when an acid is added to it?

  Water acts as a base by accepting a proton
• What is the ionic product of water (K$_W$)?


  • K$_W$ is the equilibrium constant for the dissociation of water.
  • It represents the concentration of H$^+$ and OH$^-$ ions in pure water.
• What is the expression for the ionic product of water (K$_W$)?


  K$_W$ = [H$^+$][OH$^-$]
• Why can the concentration of water be considered constant in K$_W$ calculations?


  Because water dissociates very weakly compared to its concentration
• What are the units of K$_W$?


  moles$^2$ dm$^{-6}$
• What is the significance of the position of equilibrium in acid-base reactions?

  • It determines the strength of the acid or base.
  • It influences the concentration of H$^+$ or OH$^-$ ions in solution.
• How does the percentage increase of a person's wealth compare to that of a millionaire?

  The percentage increases significantly higher for someone who is not a millionaire.
• Why can the effects of water be ignored in certain calculations?

  Because water is assumed to have a constant value relative to other ions.
• What is the new constant called when multiplying the constants $K_C$ and the concentration of $H_2O$?


  The new constant is called $K_W$, the ionic product of water.
• What is the value of $K_W$ at a given temperature?


  The value of $K_W$ is $1 \times 10^{-14} \text{ moles}^2 \text{ dm}^{-6}$.
• What are the units of $K_W$?


  The units of $K_W$ are moles squared per decimeter to the minus six.
• How does the value of $K_W$ change with temperature?


  The value of $K_W$ changes if the temperature changes.
• What is the relationship between the concentrations of $H^+$ and $OH^−$ ions in pure water?


  The concentration of $H^+$ ions equals the concentration of $OH^−$ ions.
• What simplification can be made regarding the $K_W$ expression in pure water?


  In pure water, $K_W =$$[H^+]^2$.
• What does pH measure?

  pH measures the concentration of $H^+$ ions in solution.
• What is the equation to calculate pH?

  The equation is $pH =$$-\log_{10}[H^+]$.
• How do you calculate the pH of hydrochloric acid with a concentration of $0.003 \text{ moles per dm}^3$?


  Use the equation $pH =$$-\log_{10}(0.003)$ to find $pH =$$1.5$.
• What assumption is made about hydrochloric acid when calculating its pH?

  It is assumed that hydrochloric acid dissociates fully.
• How do you calculate the concentration of $H^+$ ions from a pH of 1.7?


  Use the equation $[H^+] =$$10^{-pH} =$$10^{-1.7}$.
• What is the concentration of $H^+$ ions in nitric acid with a pH of 1.7?


  The concentration is $0.020 \text{ moles per dm}^3$.
• What is the characteristic of monoprotic acids?

  Monoprotic acids produce one $H^+$ ion for every molecule of acid.
• How do you calculate the pH of $0.25 \text{ moles per dm}^3$ of hydrochloric acid?


  The pH is $1.6$.
• What is the characteristic of diprotic acids?

  Diprotic acids produce two $H^+$ ions for every molecule of acid.