IB Chemistry HL 3.4.8 Complex Ions Question Bank

Practise IB Chemistry HL 3.4.8 with questions identifying ligands, central metal ions and electron-pair donation in complex ions.

Exam points

identify the central transition-metal ion and every ligand inside the coordination sphere
describe each ligand as donating a lone pair to form a coordination bond to the metal
use ligand charges and overall complex charge to verify the metal oxidation state

[Maximum number: 2]

Phosphoryl chloride, $\mathrm{POCl}_{3}$ , is a dehydrating agent.

$\quad \mathrm{PCl}_{3}$ and $\mathrm{Cl}^{-}$ can act as ligands in transition metal complexes such as $\mathrm{Ni}\left(\mathrm{PCl}_{3}\right)_{4}$ and $\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{3} \mathrm{Cl}_{3}\right]$ .

Define the term ligand.

6. (a) $\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=\frac{K_{\mathrm{w}}}{\left[\mathrm{OH}^{-}\right]}=\frac{\left(1.00 \times 10^{-14}\right)}{\left(3.98 \times 10^{-3}\right)}=2.51 \times 10^{-12}\left(\mathrm{moldm}^{-3}\right)$ ;
$\mathrm{pH}\left(=-\log \left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=-\log \left(2.51 \times 10^{-12}\right)\right)=11.6 ;$

OR
$\mathrm{pOH}=\left(-\log \left(5.98 \times 10^{-3}\right)=\right) 2.4$ ;
pH=(14.00-2.40)=11.6;

Marking guidance:

Award [2] for correct final answer.
Allow correct use of $\mathrm{H}^{+}$ instead of $\mathrm{H}_{3} \mathrm{O}^{+}$ throughout.

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3.4.8—Complex ions question 1