pH and buffers

• What are some bonds that holds the tertiary bonds


  Hydrogen bonds and ionic bonds
• Why is the shape of the tertiary structure of protein is considered important


  Does determine the protein activity/function e.g protein
• Give the Brønsted-Lowry definition of Acid



  A compound that donates a hydrogen ion
• Give the Brønsted-Lowry definition of Base


  A compound that accepts a hydrogen ion
• Write a general equation of dissociation of an acid

  HA⇌ A- + H+
• Write a general equation of dissociation of a base

  B + $H^+$ ⇌ $BH^+$
• Write an equilibrium equation when HCl reacts with water and explain the products existed:

  HCl + H2O ⇌ H3O+  +  Cl-

  
  

  HCl releases a hydrogen ion in solution. $H^+$are too unstable to exist individually, it become stabilised once it binds to water. So Water accepts the hydrogen ion, hence act like a base
• What is the name of the molecule when H+ reacted with water and state its formula

  A hydronium ion (H3O+)
• Write an equilibrium equation when NH3 reacts with water and explain the products existed

  NH3 +H2O ⇌ OH- + NH4+

  In this case: H2O acts like an acid, hence donates H+ to the ammonia
• True or false: Acid and base can exist without eachother.


  False: they cannot exist in isolation
• Write the general equation for acid-base reactions


  HA + B ⇌ A-  +  BH+
• What the name which water can be described as when it acts like an acid or a base?

  An amphoteric compound
• True or false: Dissociation of acids or bases always reaches a point of equilibrium


  True.
• How long does it occur for the dissociation of acids/bases to happen in aqueous solution?


  Almost instantly
• What could be determined when the readiness of an acid to dissociate or the readiness of a base to associate is known?


  The strength of acid/base
• State the difference between strong and weak base in terms of hydroxide or hydrogen ions

  A strong base readily accepts H+ (or readily dissociates to form OH-)

  
  

  A weak base poorly accepts H+ (or only partially dissociates to form OH-)
• What's the symbol for acid dissociation constant?

  Ka
• What's the generic equation for Ka


  Where [A-] is the concentration of the conjugated base

  and [HA] is the concentration of the acid

  
• How do you determine the strength of an acid using the Ka?


  If Ka>1, then that's a strong acid

  If Ka<1, then that's a weak acid
• What condition is needed to neglect the concentration of water off the Ka equation?


  The concentration of water is very large and invariant (55.5M)
• What's the generic equation for Kb?


  Equation:

  
• What does Kb stand for:


  Base dissociation constant
• Write an equation linking pKb and Kb


  pKb= -log (Kb)
• What the symbol of the ionic product of water?

  Kw
• What is Ka a measure of?


  The extent of acid dissociation to form hydronium ions and a conjugate base in water
• Wite an equation linking pH and H+?


  pH = -log10 [H+]
• What's pH a measure of?


  the concentration of hydrogen ions (or simply hydrogen ions).
• What is buffer consist of?


  Weak acid and its conjugated base
• Why is buffer considered important?


  It minimises the change in pH
• Write the Henderson-Hasselbalch equation


  pH=pKa +$log [A^-]/$[HA]
• Give some example on what can be used for measuring pH?

  Litmus paper, litmus paper