Zadanie 1b, Paper 2, listopad 2025, TZ1, Chemia IB HL
Wzorowane na: Chemistry HL Paper 2, November 2025, TZ1, pytanie 1(b). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Wspólne informacje do wiązki zadań
Sulfur is an element present in two of the amino acids from which proteins are built.
Polecenie
4.81 g of sulfur was heated in a stream of chlorine gas until the reaction was complete. The mass of the chloride produced was 10.13 g.
(i) Calculate how many atoms are present in this 4.81 g sample of sulfur. Use sections 2 and 7 of the data booklet.
(ii) Determine, showing your working, the empirical formula of the chloride formed. Use section 7 of the data booklet.
(iii) It was found that the chloride formed in (b)(ii) has a relative molecular mass of 135.04. Using this value, determine its molecular formula, showing your working. Use section 7 of the data booklet.
(iv) This chloride of sulfur has a melting point of 193 K. With reference to its structure and bonding, outline why this melting point is low.
(v) The character of the bond formed between sulfur and chlorine can be read from electronegativity data. Describe this bond's nature. Use sections 9 and 17 of the data booklet.
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Odpowiedź z klucza
(i) nS = «4.81 g ÷ 32.07 g mol−1 =» 0.150 «mol»; number of atoms = «0.150 mol × 6.02 × 1023 mol−1 =» 9.03 × 1022 ✔
(ii) mCl = «10.13 − 4.81 =» 5.32 «g»; nS = 0.150 «mol» AND nCl = «5.32 g ÷ 35.45 g mol−1 =» 0.150 «mol» ✔
ratio S : Cl = «0.150 : 0.150 =» 1 : 1 ✔
SCl ✔
(iii) «M(SCl) = 32.07 + 35.45 = 67.52 g mol−1; 135.04 ÷ 67.52 = 2» S2Cl2 ✔
(iv) simple molecular «structure» AND covalent «bonding within the molecules» ✔
«only» weak intermolecular forces / London dispersion forces / dipole–dipole forces «have to be overcome on melting» ✔
(v) electronegativity difference = «3.2 − 2.6 =» 0.6 AND average electronegativity = «(3.2 + 2.6) ÷ 2 =» 2.9 ✔
«weakly polar» covalent ✔
Schemat punktowania
(i) [1] for 9.03 × 10²² (accept 9.02 to 9.03 × 10²²). (ii) M1: amounts of S and Cl in mol (mass of chlorine obtained by difference); M2: simplest ratio 1 : 1; M3: SCl. Award [1] for SCl with no working. (iii) [1] for S2Cl2; working must be shown. (iv) M1: simple molecular and covalent; M2: weak intermolecular forces. (v) M1: both the difference 0.6 and the average 2.9; M2: bond type read from the bonding triangle: covalent (accept polar covalent).
Komentarz. The bond lies in the covalent region of the van Arkel–Ketelaar triangle (about 85 % covalent character), close to the polar covalent boundary; the marking point is the correct reading of the triangle, not the adjective.