Chapter 20 quizlet

• What is the difference between a base and an alkali?

  An alkali is soluble.
• What is a Brønsted-Lowry acid?

  Species that donates a proton
• What is a Brønsted-Lowry base?

  Species that accepts a proton
• What is a conjugate acid-base pair?

  Two species that can be inter converted by the transfer of a proton

  
• How do you identify a conjugate acid?

  In the reverse reaction, which species will donate an proton?

  
• How do you identify a conjugate base?

  It will loose a proton

  
• When water acts as a base, what is produced?

  A hydronium ion, H3O+ (aq)

  
• What is the active acid ingredient in any aqueous acid?

  The hydronium ion, H3O+ (aq). It is far more commonly expressed as H+.
• What is a monobasic acid?

  A proton donor in which one hydrogen ion can be replaced per molecule by a metal or ammonium ion in an acid-base reaction.
• What is a dibasic acid?

  A proton donor in which two hydrogen ions can be replaced per molecule by metal or ammonium ions in an acid-base reaction
• What is a tribasic acid?

  A proton donor in which three hydrogen ions can be replaced per molecule by metal or ammonium ions in an acid-base reaction
• What type of acid is HCl?

  Monobasic/monoprotic
• What type of acid is CH3COOH?

  Monobasic/monoprotic.
• What type of acid is H2CO3 (carbonic acid)?

  Dibasic/diprotic
• What type of acid is H3BO3 (boric acid)

  Tribasic/triprotic
• How can knowing the number of hydrogens in an acid help to work out the volume of base needed to neutralise it?

  A dibasic acid will need double the volume of the same base used to neutralise a monoprotic acid.

  A tribasic acid will require triple.
• How is an ionic equation written?

  Split the aqueous species into ions. Anything that is not aqueous is left as it is.

  Remember to write the state symbols for all species.

  Cancel the spectator ions.

  Rewrite equation.
• What is a spectator ion?


  An ion that appears on both sides of an equation and does not change in the reaction.
• General formula for reaction of acids with metals

  Acid + Metal -> Salt + Hydrogen
• What is the general formula for reaction of acids with carbonates?

  Acid + Carbonate -> Salt + Carbon dioxide + Water
• What is the general formula for reaction of acids with metal oxides?

  Acid + Metal oxide -> Salt + Water
• General formula for reaction of acids with alkalis

  Acid + Alkali -> Salt + Water
• What is the range of hydrogen ion concentrations on Sorenson's pH scale from most acidic to least?

  Hydrogen ion concentrations of 10^-1 (acidic) TO 10^-14 (alkali)
• The pH scale is logarithmic- what does this mean?

  A change in one pH number is equal to 10x difference in [H+(aq)].

  A solution of pH 1 contains 10^13 more Hydrogen ions than a solution of pH 14
• What does a low hydrogen ion concentration indicate?

  A high pH
• What does a high hydrogen ion concentration indicate?

  A low pH
• How do you calculate pH from [H+(aq)]?

  pH = -log[H+(aq)]

  
• How do you calculate [H+(aq)] from pH?

  [H+] = 10^-pH

  
• What is a strong acid?

  Strong acids dissociates completely in water (solution). All acid particles dissociate to release H+ ions.

  HA (aq) ------> H+ (aq) + A- (aq)
• How can the pH of a strong acid be calculated?

  HA (aq) ------> H+ (aq) + A- (aq)

  For a strong acid, the [H+(aq)] is equal to the concentration of the acid {HA (aq)] as all the acid dissociates.

  The pH of the acid can be calculated directly from the concentration of the acid using

  pH = -log[H+(aq)]
• How can you calculate the change in pH of a strong acid after it has been diluted?

  Calculate the concentration of acid before dilution, and after. This is equal to [H+].

  Use these values in pH = -log[H+(aq)]

  Compare pH values to see how much the pH values have changed.
• What is the acid dissociation constant (Ka)?

  It is version of Kc used to show the extent of acid dissociation at equilibrium.
• What is a weak acid?

  An acid which partially dissociates in water. It is shown by the general equation

  HA (aq) ⇌ H+ (aq) + A- (aq)
• How is Ka calculated?

  Ka = [H+][A-]/[HA]

  
• What are the units for Ka?

  Everything is moldm-3.

  Cancel top and bottom, invert if needed.
• How to calculate Ka for weak acids

  Ka = [H+]^2/[HA]
• What temperature are Ka values standardised at?

  25C as Ka changes with temperature, as do all equilibrium constants.
• The larger the Ka value...

  The greater the dissociation, the greater the acid strength, the further the equilibrium is to the right.

  The concentration of the dissociated ions on the top are larger.
• Why are pKa values more useful than Ka values?

  pKa values are more manageable and it is much easier to compare relative acidic strength using pKa than Ka. This is because Ka has numbers with negative indices, but pKa does not.

  pKa is used for comparing strengths of weak acids particularly in biological systems.
• How can Ka be converted to pKa?


  pKa = -logKa