Acids Bases And Ph Flashcards
Bronsted Lowry‘s model for acids and bases
Bronsted Lowry‘s acid is a proton donor
Bronsted Lowry‘s base is a proton acceptor
Monobasic acid
Has one hydrogen ion per molecule that can be replaced by metal ions or ammonium during neutralisation
Dibasic acid
Has two hydrogen ions per molecule that can be replaced
Tribasic
Three hydrogen ions can be replaced per molecule by metal ions or ammonium ions to form a salt
Conjugate acid-base pairs
They contain two species that can be interconverted by transfer of a proton
Conjugate acid
The acid that donates a proton to a base
Conjugate base
Base that accepts A proton from an acid
What condition is required for dissociation to take place
The presence of water
H30+ is also known as
The hydronium ion
pH definition and mathematical expression
pH is a measure of the concentration of H+ ions in solution
pH= -log[H+(aq)]
A small value of pH suggests there is a ….. concentration of H+ ions
Large
So it is quite acidic
On the base 10 logarithmic scale , a change in pH by one unit is equivalent to
A 10x change in the concentration of hydrogen ions
Mathematic expression for the concentration of hydrogen ions(the formulae ) from the ph
[H+(aq)]= 10^-pH
For a strong monobasic acid , what is the ratio of moles of the acid to the hydrogen ions and what does this suggest
1:1
It suggests that the concentration of the acid and hydrogen ions are the same
Acid dissociation constant symbol
K little a(Ka)
The further right the position of equilibrium of in weak acid
The stronger the weak acid
Formulae of pKa
pKa= -logKa
Formulae for Ka using pKa
Ka = 10^-pKa
Are acids with a Ka value or pKa value weak or strong
They are weak
What are the two approximations for weak acids
The concentration of hydrogen ions is the same as the concentration of the conjugate base
[H+]= [A-]
The concentration of the acid at equilibrium is equal to the concentration of the acid at the start
What does Kw stand for
The ionic product of water
Formulae for Kw
Kw = [H+][OH-]
Is Kw temperature dependent?
What is Kw at 298K or 25degrees
Yes
1*10^-14mol^2dm^-6
Water is neutral , what does this imply during dissociation of water
It implies that
[H+]= [OH-]
What happens to the ph value of the neutral point when temperature changes and why
It changes as well
Because Kw is temperature dependent
Approximation for strong monobasic acids
[HA]= [H+]
Formular to find new concentrations of acid
Original concentration * (volume of reagent/total volume)
The larger the Ka value, the ……. The weak acid
Stronger
The smaller the pKa value, the…. The weak acid
Stronger
Pure water is neutral at any temperature , true or false
True
Two requirements to calculate the ph of a strong base
The concentration of the base
The ionic product of water
