Zadanie 8c
Wzorowane na: Chemistry HL Paper 2, May 2023, TZ2, pytanie 8(c). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 8b-8c.
Metal halides are ionic compounds that form crystal lattices in the solid state and dissolve in water to give aqueous ions.
Polecenie
Nickel forms the chloride NiCl2.
(i) State the full electron configuration of the nickel(II) ion, Ni2+.
(ii) In aqueous solution nickel(II) ions exist as [Ni(H2O)6]2+, which is green. Describe the interaction between the nickel ion and a water molecule in terms of the type of bond and how this bond is formed.
(iii) When aqueous ammonia is added in excess, the violet-blue complex ion [Ni(NH3)6]2+ is formed. Explain why different ligands give different colours of complex.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) 1s2 2s2 2p6 3s2 3p6 3d8 ✔
(ii) type of bond: coordination / dative covalent bond ✔
how the bond forms: the water molecule «oxygen atom» donates a lone pair of electrons to the nickel(II) ion «into an empty orbital» ✔
(iii) the ligands split the d orbitals by an energy gap, ΔE, that differs from ligand to ligand ✔
the gap determines the wavelength / colour of light absorbed «when an electron is promoted to a higher d orbital», so the colour transmitted differs ✔
Schemat punktowania
(i) [1]; 4s electrons are lost before 3d, so 3d8 with no 4s. (ii) M1: coordination / dative covalent; M2: ligand donates an electron pair. Accept covalent for M1 only if the pair origin is stated in M2. (iii) M1 needs a reference to the different energy gap or splitting of the d orbitals; M2: the energy absorbed corresponds to a different wavelength of light / colour.