1.12 Acids and Bases
No description yet. This curated deck is ready for daily study.
Card preview (24)
What is the Brønsted-Lowry classification of an acid?
Proton donor
What is the Brønsted-Lowry classification of a base?
Proton acceptor
What is a strong or weak acid?
Strong acids completely dissociate (ionise) Weak acids partially dissociate (ionise)
What are some strong and weak acids?
Strong: Sulfuric acid Hydrochloric acid Nitric acid Phosphoric acid Weak: Carboxylic acid
What are some strong and weak bases?
Strong: Hydroxide Weak: Ammonia Amines
What is a conjugate acid/base?
Formed from an acid/base Conjugate base - species formed when an acid lost a proton Conjugate acid - species formed when a base gained a proton
What word is significant for acids and bases?
Amphoteric A species can act as an acid or a base
What is significant about water?
It is amphoteric and self protonating (always contains some H+ ions and OH-) It is weakly dissociated
What are the types of acids that fully dissociate?
Monoprotic - for each acid molecule = 1H+ ion Diprotic - for each acid molecule = 2H+ ion
How do you know what type of ‘protic’ a base is?
Monoprotic - takes only 1H+ ions to neutralise the 1OH- Diprotic - takes 2H+ ions to neutralise the 2OH-
What is the equation for pH?
pH = -log[H+] pH is always 2 dp!!!!!
What is the equation for H+ concentration?
[H+] = 10 ^-pH
What is Kw?
Another constant that incorporates Kc and [H2O] Determined from pure water
What are some Kw equations?
Kw = [H+][OH-] Or Kw = [H+]^2 So [H+] = Kw/[OH-]
What is Kw?
Kw = 1x10^ -14
What do you have to remember working out pH or H+ conc?
If the acid/base is monoprotic or diprotic! You might need to multiply or divide by 2 or 4 depending on the direction of the dissociation (so use the equation as well - or make one)
How do we work out partial neutralisation calculations?
Find the moles of the acid and base Find which is in excess (consider the ‘protic’ - multiply by 2? Before decision Which ever is in excess take one from the other Excess moles / total volume = conc of excess If acid - find the pH If base - use Kw to find [H+] and the find the pH In Q’s look for ‘solution’
How do you decide which is an acid/base and or conjugate?
Use the definitions Look in the correct direction of the reaction for that compound
What is significant about weak acids?
They only weakly dissociate in aqueous solutions
How is a weak acid equation represented?
HA ⇌ H+ + A- H - the hydrogen ion A - the undissociated negative ion in the weak acid
What is Ka?
The weak acid dissociation constant Ka = [H+] [A-] ————— [HA] Units = mol dm-3
What is the relationship between Ka and equilibrium?
The greater value of Ka The equilibrium is further to the right The greater the dissociation The greater the weak acid Therefore a lower pH (more H+ ions)
How do you work out H+ using Ka?
[H+] = square root of Ka x [HA]
What are the equations to move between Ka and pKa?
pKa = -log Ka Ka = 10 ^-pKa