5.1.3 Acids, Bases and Buffers Flashcards
acids dissociate and release ….
H+ ions
Alkalis dissociate and release…..
OH- ions in solution
Bronsted-Lowry Acid
a species that donates a proton
Bronsted- Lowry base
species that accepts a proton
conjugate acid-base pairs
an acid and a base that can become each other through the transfer of a H+ /proton
Hydronium ion
monobasic
when one mole of acid dissociates to form one mole of H+ ions/protons
acids that release one proton into solution. Has one H that can be replaced.
example of mono basic acids
HCl, CH3COOH
dibasic acid, example
when one mole of acid dissociates to form 2 moles of H+/ protons
An acid that contains two replaceable hydrogen atoms per molecule of the acid - produces 2 H+ ions
H2CO3, H2SO4
tribasic
when one mole of acid dissociates to form 3 moles of H+/protons
why is CH3COOH mono basic ?
organic acids don’t replace any hydrogen atoms from the carbon chain
acid + carbonate
salt and water and co2 (carbonates are bases)
acid + metal
salt + hydrogen
why is solid carbonate included in the ionic equation?
2H+ + CuCO3 (s) —> Cu 2+ (aq) + H20(l) + CO2 (g)
it changes state to a gas, which is included in an ionic equation
what does pH measure?
the concentration of H+ ions in solution
hydrogen ion concentrations have a large range of values, what method makes it a more manageable scale?
negative log (10^-)
equation to find pH from H+ concentration
pH = -log (H+)
equation to find H+ ion concentration from pH value
[H+] = 10 to the minus pH
how does a change in pH by 1 affect H+ ion concentration?
x 10 difference
How would you dilute a solution from 1 to 4 pH?
changes by pH of 3 so dilute by 10x10x10 = 1000 times
How many more H+ ions does a solution of pH 1 have compared to ph 14?
10 to the power of 13
when calculating pH of a strong, monobasic acid, why is H+ equal to the concentration of the acid?
amount of H + ions determines concentration and if strong acids completely dissociate their H+ ions , thats equal to concentration
What is the version of the equilibrium constant used in acid-base equilibria?
acid dissociation constant (Ka)
What does the Ka value measure?
the amount a weak acid dissociates. strong acids fully do.
formula of Ka?
Ka = concentration of products / concentration of reactants
what does a larger Ka value mean? and why?
more dissociation so stronger acid, because for equilibrium to be further right, number at top (concentration of ions) needs to be bigger than bottom (concentration of acid)
what factor changes equilibrium constant Ka?
temperature - affects all equilibrium constants
Ka values are hard to compare, so what negative algorithm value is used?
pKa
pKa =
-log Ka
How can you find ka from pKa?
10 to the -pKa
compare the size of ka and pKa in a strong acid
stronger the acid, larger Ka value because more dissociation, smaller the pKa
compare the size of Ka and pKa in a weak acid
weaker the acid, smaller the Ka, bigger the pKa
water acts as both an acid and as a abase, show its acid base equilibrium
H20 + H20 —> H30+ + OH-
what is the acid dissociation constant for water?
Ka = [H+ (aq)] [OH- (aq)] / [H2O(l) ]
weak acids partially dissociate, how is that shown?
through arrow going both ways (equilibrium arrow)
What is Kw?
Ionic product of water - the ions in water H+ and OH- multiplied together
equation for Kw?
Kw = [H+][OH-]
in aqueous solution there will always be both H+ and OH- ions in solution. However, when there are more H+ ion, it is …
acidic
in an acid solution with pH 4, what is the concentration of OH- ions?
10 to the power of -10 because concentrations of H+ and OH- add up to -14 (kw value)
How do you find the pH of a strong base?
use kw - find H+ concentration and ionic product of water value to find OH-
How is finding the pH of a mono basic base and dibasic base different?
have to multiply number of OH+ ions by 2 because its a dibasic base so produces two moles of OH- ions
when there are two acids in a reaction, How do you know which acids as a base or acid?
the strongest acid will act as the acid (bigger Ka value etc ) and other as the base
