Core 1- Acids and bases Flashcards
Give a definition and example of arrhenius acid and arrhenius base
Arrhenius acid- ionises in water to give H+ and anions
HCl⇒ H++Cl-
Arrhenius base- ionises in water to give OH- and cations.
NaOH⇒ Na+ + OH-
Give a definition of Bronsted Lowry acid and base and give example of each.
Bronsted Lowry acid- proton donor
CH3COOH + NaOH ⇒ Na+CH3COO- + H2O
Bronsted Lowry base- proton acceptor
NH3 + H2O ⇔ NH4+ + OH-
What is lewis acid and lewis base. Give an example of each.
Lewis acid is electron pair acceptor
BF3 + NH3 ⇒ BF3<——NH3
Tranisition metal is also lewis acid
Lewis base is an electron pair donor.
BF3 + NH3 ⇒ BF3<——NH3
ligands in transition metal complex
What happens during a neutralization reaction?
Proton is transferred from acid to a base to produce water and give a salt. This reaction is exothermic
Which species contribute to acidity?
Hydroxonium ion (H3O+)
H+ doesn’t exist on its own and it solvates.
What is conjugate acid?
Conjugate acid is base plus a proton
What is conjugate base?
Acid minus proton.
What is acid ( or base) strength?
It is tendency of an acid to give a proton (or accept a proton). It is governed by equilibria reactions.
What is strong acid?
Acid which fully dissociates in a solvent.
What is weak acid?
Acid that partially ionizes in a solution.
What is Ka and its units?
Ka= ( [H3O+][A-] )/[HA]
moldm^-3
What is pKa? Why is it used over Ka?
pKa=-log(Ka)
This is used because Ka values are often very low or very big.
Describe solvent levelling.
Solvent levelling is the idea that we can’t discriminate between the strongest acids or bases if sufficiently basic or acidic solvent is used.
Much weaker base or acid would be used to find discriminate between them. Solvent determines acidity of our acid.
What is pH? What happens to pH when H+ increases?
pH= -log[H+]
When H+ increases, pH becomes lower. When H+ decreases, pH becomes higher.
What is pOH? What happens when we increase OH concentration?
pOH= -log[OH]
As we increase concentration of OH-, pOH decreases and when we decrease concentration of OH-, pOH increases.
What is Kw?
Kw=[OH-][H3O+]
1 x 10^-14 mol^2dm^-6
Give two relationships:
- between pOH, pH and pKw
- between pKa, pKb, pKw
pOH + pH= pKw
pOH + pH= 14 at 298K
pKa + pKb= pKw
pKa + pKb=14 at 298K
What is a buffer solution?
Buffer solution is the solution that resists small changes in pH when small amount of acid or base is added.
How is base solution prepared?
Base solution is prepared from a weak base and its conjugate acid (salt) or weak acid and its conjugate base (salt).
Will weak acid reacting with strong base require the same amount to neutralise it as strong acid reacting with same strong base?
Yes, because they react in 1:1 ratio.
What is Henderson Hasselbalch equation?
What is equivalence point?
Equivalence point is the point at which equal amount of acids and bases are added so that they are both neutralised.
What is an end point?
End point is the point at which the indicator changes colour. It should be the same as our equivalence point ideally.
What is pH indicator? What is it used to monitor and how is it chosen?
pH indicator is a weak acid or a weak base wihch has differently coloured neutral and ionic forms. As pH changes by 1 unit, it goes through complete colour change.
It is used to check when titration is complete to find accurate concentration of our unknown solution. It is chosen so that the pKa=pH at equivalence point.
What is mono, di, tri protic acid?
monoprotic acid has one H+ to donate
diprotic acid has 2 H+’s to donate
triprotic acid has 3 H+’s to donate
As we start to remove more H+ from an acid, pKa becomes
HIGHER
What is speciation curve?
Speciation curve shows us how does the concentration of different ions vary at different pH. Before next deprotonation starts, first acid needs to fully deprotonate.
What is the property of amino acids?
Amino acids are amphoteric (amino group and carboxylic group).
Depending on pH, overall charge on an amino acid will change.
What is zwitterion and isoelectronic point?
Zwitterion is the amino acids that has equal number of negative and positive charges. It has zero charge overall.
Isoelectronic point is the pH at which we have zwitterion.
