Reactions of ions in solution Flashcards
(16 cards)
what pH do 2+ complex ions have?
pH 5/6
what pH do 3+ complex ions have?
pH 1-3
examples of 2+ complex ions need to know?
[Cu(H2O)6]2+
[Fe(H2O)6]2+
examples of 3+ complex ions need to know?
[Al(H2O)6]3+
[Fe(H2O)6]3+
why are metal-aqua ions acidic?
- positively charged ion draws coordinately bonded pair of electrons towards it
- this causes the O atom in H2O to draw the O-H bonding pair of electrons towards it
- this creates a more polar dipole across the O-H and causes it to weaken
- H+ dissociates from the complex
in the equation showing the dissociation of the H+ from the 2+ complex, where does the position of equilibrium lie?
quite far left
in the equation showing the dissociation of the H+ from the 3+ complex, where does the position of equilibrium lie?
further right
why are 3+ ions more acidic than 2+ ions?
3+ ions have a greater charge density, so cause an even greater dipole and therefore greater dissociation and a lower pH.
REMEMBER: both 2+ and 3+ ions only lose 1 H+, but position of eq liies further right for 3+ ions, so they are more likely to release an H+, making them more acidic
what would you expect to see when NaCO3 is added to a 3+ complex ion, why?
effervescence - behaves like an acid
what does amphoteric mean?
shows both acidic and basic properties
what is the name for when something shows both acidic and basic properties?
amphoteric
what equation shows that aluminium hydroxide can act as a base?
Al(H2O)3(OH)3 + 3HCl (aq) —-> [Al(H2O)6]3+ (aq) + 3Cl- (aq)
accepts H+ of HCl therefore acts as base
what colour is aluminium hydroxide?
white solid
what equation shows that aluminium hydroxide can act as an acid?
Al(H2O)3(OH)3 + OH- (aq) —-> [Al(OH)4]- (aq) + 3H2O (l)
accepts electron pair from OH- therefore acts as acid
