DM3

Question 1

if light in the visible region of the spectrum is absorbed then…

Answer 1

the comound will appear coloured

Question 2

colour in aq solution of:

• Fe2+
• Fe3+
• Cu+
• Cu2+

Answer 2

• Fe2+ = green
• Fe3+ = orange / brown
• Cu+ = unstable in aq. solution
• Cu2+ = blue

Question 3

transition metals compounds are mostly coloured so can aso be used in…

Answer 3

QUALITATIVE analysis

Question 4

Fe2+(aq) + 2OH-(aq) –>

Answer 4

Fe(OH)2(s)

green GELATINOUS precipitate

Question 5

if the source of hydroxide ions is AMMONIA, the pale blue precipitate of Cu(OH)2 will re-dissolve on addition of excess ammonia to give a….

Answer 5

deep blue-purple solution

= solution contains copper/ammonia complex ion (DM6)

Question 6

what happens when a compound absorbs light?

Answer 6

• light absorbed only if energy of light matche energy gap between 2 energy states in the atom
• if it does electron promoted lower to higher energy orbital
• ground state –> excited state

Question 7

what hapens when a d-block compound absorbs light?

Answer 7

• freq. (v) of light absorbed depends on energy difference (_E) between these 2 levels
• 5 d-orbitals
• but LIGANDS surrounding metal atom/ion cause these orbitals to split in such a way that some are slightly higher in energy than others
  -(_E) now = light absorbed fas in visible part spectrum
• transmitted light is that which isnt absorbed = colour seen
  (coloured glass + solutions)