Zadanie 3b
Wzorowane na: Chemistry HL Paper 2, May 2026, TZ3, pytanie 3(b). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 3a-3e.
Metals and their compounds are used in construction, in batteries and as pigments.
Polecenie
(i) Outline why the strength of the metallic bond increases from potassium, K, to calcium, Ca.
(ii) Write an equation for the reaction of potassium, K, with water, including state symbols.
(iii) Outline why the electronegativity of chlorine is greater than that of iodine.
(iv) The first ionization energy of rubidium, Rb, is 403 kJ mol−1. Determine the wavelength corresponding to the limit of convergence for one atom of rubidium, in m, and the region of the electromagnetic spectrum to which it belongs. Use sections 1, 2 and 5 of the data booklet.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz CKE i punktacja
Odpowiedź z klucza
(i) Any two of:
calcium has a smaller «ionic» radius ✔
calcium has more delocalized electrons «two per atom, against one for potassium» ✔
calcium has the greater «ionic» charge «2+ against 1+» ✔
(ii) 2 K(s) + 2 H2O(l) → 2 KOH(aq) + H2(g)
correct products AND state symbols ✔
correct balancing ✔
(iii) chlorine has fewer occupied energy levels / less shielding «than iodine»
OR
chlorine has its valence electrons closer to the nucleus
OR
chlorine has the smaller atomic radius ✔
(iv) «E = 403 000 J mol−1/6.02 × 1023 mol−1 =» 6.69 × 10−19 J ✔
«λ = hc/E = (6.63 × 10−34 J s × 3.00 × 108 m s−1)/6.69 × 10−19 J =» 2.97 × 10−7 m ✔
Region: ultraviolet / UV ✔
Schemat punktowania
(i) [2 max]; accept "calcium has more valence electrons" for the electron mark. (ii) M1: correct formulas of the products with state symbols (ignore (aq) versus (s) for the hydroxide only if the equation is balanced); M2: balanced. (iii) [1]; accept "chlorine has the smaller atomic radius". (iv) M1: energy of one atom (the division by the Avogadro constant, and the conversion from kJ); M2: wavelength in m; M3: UV. ECF from M1.