Inorganic chemistry Flashcards
What is a positively charged ion known as?
Cations
What is a negatively charged ion known as?
Anions
What are zwitterions?
Both anions and cations – cations at low pH and anion at high pH
What does the Bronsted-Lowry theory state?
An acid is a proton donor
A base is a proton acceptor
What do monovalent, divalent, trivalent mean in terms of cations?
They have 1, 2 and 3 electrons to lose, respectively
What is a proton?
Hydrogen ion – lost electron (H+)
What happens when vinegar is put into water?
Proportion of hydrogen ions will dissociate = acetate and NH+
– Reversible action
– Acetate is now base
–Acetic acid is an acid
What is true of bases?
Any base (HB+) can dissociate into hydrogen ions and conjugate base (reversible)
What is pH?
Measure of the concentration of protons in solution
What does more protons mean in terms of pH?
+ protons = lower pH
What do less protons mean in terms of pH?
less protons = higher pH
What is the equation for pH?
pH = log10 1/[H+] = -log10[H+]
What is the pH of pure water?
7
What is an example of a strong acid?
In aqueous solution, HCl is almost completely dissociated
–1M solution has a pH of 0
What is an example of a weak acid?
In aqueous solution, HCl is ~0.4% dissociated and is thus a weak acid
–1M solution (vinegar) has pH of ~2.5
How is acid strength measured?
Measured according to the pKa of the acid
What is the pKa of the acid?
The pH at which the concentration of acid and conjugate base are equal
– As it can exist in 2 forms (acid and conjugate base) there is a point at which it is half-base/half-acid
What does a lower pH mean (acids)?
More acid form / less conjugate base form
What does a higher pH mean (acids)?
Less acid form / more conjugate base form
What is multiple ionisation?
Not every dissociation of proton is the same
–e.g. phosphoric acid can lose 1/2/3 protons to gain respective charges
What is true of acids and bases around their pKa?
Acids and their conjugate bases can act as buffers of H+ around their pKa
What do buffers do?
They act to reduce the possibility of big pH changes when [H+] changes
