Acids And Bases Flashcards
What is a bronsted Lowry acid
A substance that can donate a proton
What is a bronsted Lowry base
A substance that can accept a proton
What is the equation for calculating pH
pH = -log[H+]
Difference between strong acids and weak acids
Strong acids completely / fully dissociate
Weak acids only slightly dissociate into their ions
What is the concentration of hydrogen ions in a monoprotic acid
The same as the concentration of the acid
What is Kw
What is the formula
The ionic product of water
Kw = [H+] [OH-]
What is the standard value of Kw
(Units)
1 x 10^-14 mol2dm-6
What type of reaction is the dissociation of water
Endothermic
What do we assume when calculating ph of pure water
That the concentration of hydrogen ions is equal to the concentration of OH - ions
How do we calculate the pH of strong bases
Use the kw expression to work out the concentration of hydrogen ions
And then use that to calculate the ph
What is the equilibrium equation for weak acids
HA -><- H+ + A-
What is the weak acid dissociation expression
Ka = [h][a] / [ha]
How do you calculate pKa and Ka from each other
pKa = -log aka
Ka = 10^-pka
What are 2 assumptions when calculating the ph of a weak acid
That H conc is the same as A - conc since they dissociate with 1:1 ratio
That concentration of HA is constant
What is the simplied expression for Ka
[H+]^2 / (HA)
What assumption can we make at half equivalence point
That ph = pKa
And (Ha) = (h-)
What is half equivalence
When weak acid has reaction with exactly half the neutralisation volume of the alkali
What is a buffer solution
Solution where the ph doesn’t change significantly if small amounts of acid or alkali are added to it
What is an acidic buffer solution made from
A weak acid and a salt of that weak acid (made from reacting the weak acid with a strong base )
How is a basic buffer solution made
A weak base and a salt of that weak base (made from reacting weak base with strong acid)
What equation is used for calculating ph of buffer solutions
H = ka x (ha) / (a-)
Why are ph meters calibrated
They lose accuracy on storage
What indicator is used with strong bases
What’s the colour change
Phenopthaelin
Colourless acid
Pink alkali
What indicator is used with strong acids
What’s the colour change
Methyl orange
Red acid
Yellow alkali
