Understanding Acid - Base Properties Flashcards
What does the size of Ka gives indication of?
The tendency of the reaction to form products or remain as reactants
What does a large Ka value mean
Greater tendency for acid to donate a proton to water
Stronger acid
Greater degree of ionisation
Which acid would produce the most vigorous reaction
Acid with the higher H+ concentration, give faster rate of reaction
What is the acidity constant (Ka)
Equilibrium constant for reaction occurring in water
Indicator if acid strength
If Ka is large that means the Conjugate base is?
Extremely weak
If Ka is small that means the Conjugate base is
Stinger base as the acid is progressively weaker
Sting base + sting Acid =
Neutral salt
Weak base + strong acid =
Acidic salt
Weak acid + strong base =
Basic salt
Weak base + weak acid =
Neutral salt
What is auto ionisation
Ions produced in equal numbers by a reversible reaction
Solution is said to be neutral when
Water or any solution where H+ and OH- have same conc
What dies adding acid to water do?
Increase H+ conc and lowers OH- conc
What is Kw
Equilibrium constant for the ionisation if water
1.0 x 10^-14 at 25 degrees
What does Kw confirm that H and OH are
Inverely related
Increase in H, decreases OH
Increasing H by 3x, Decreases OH by 3x
Extremely small value (1x10^-14) of Kw means there’s a strong tendency of?
Water to remain in the unionised molecular form (h20) not (h and OH)
Kw is constant value but changes witg
Temp
Autoionisation of water is endothermic and by LCP higher temp will favour the formation of products
When Kw changes with temp it means that the conc of
H and OH with increase as temp increases
1 unit difference in pH represents
A 10x difference in conc of H+ (2 unit difference in pH corresponds to a 10× difference in [H]
What is a buffer
A solution that has the ability to resist pH change when either an acid or base is added
Why do buffer solutions work
Because the weak acid and base can co exist without neutralizing one another, yet can still react to neutralise any strong acid/base added
Adding bases imposes an increase of [OH] ion. What are the following things that occur
Extra OH from base will neutralise some of the h30 present in buffer solution causing conc to initially fall
Falling h30 cause equilibrium to shift right replacing most of the lost h30 and preventing its conc from falling significantly
By behaving this way, buffer solution can maintain a fairly constant pH despite imposes Change
Adding acid to a buffer solution causes the [h30] to increase. What are the following events
The imposed change cause the equilibrium to shift left
Most added h30 is consumed
Prevent [h30] from rising significantly
Buffer maintains fairly constant pH
What is a buffer capacity
Ability of a buffer solution to neutralise excess acid or base without appreciable change to its pH
2 things For buffer solution to be more effective
High conc of both weak acid and base
- ensures nether will be depleted or reduced on addition of either OH or H
Similar concentrations
What pH is blood maintained at
7.4 +/- .05
What pH is blood maintained at
7.4 +/- .05
If blood pH falls outside range it can effect
Operation of cell membranes
Alter protein structure
Prevent enzymes from functioning correctly
Blood maintains pH range with aid of what acid/ion and what are their concentrations
Carbonic acid (weak acid) [0.0254] Hydrogencarbonate ion (weak cb)[0.0012]
If excess H is present in blood its eliminated as the equilibrium shifts
Left
If h30 fall too low, equilibrium shifts
Right to produce more h30
What 2 organs help maintain blood capacity
Lungs and kidney
Whats does an increased rate of consumption of sugars do in blood buffering
Increases cellular respiration in muscle tissue which leads to an increase in [co2] in blood
Receptors in brain that are sensitive to increased [H] signal a ?
Reflex to breathe more deeply and rapidly
which means a greater Loss of co2 in lung cavity
which causes the equilibrium to shift left to PC the decreasing conc of co2 in long capillaries
