Zadanie 3c
Wzorowane na: Chemistry SL Paper 2, May 2026, TZ2, pytanie 3(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 3a-3c.
Magnesium and sodium are reactive metals with many practical uses.
Polecenie
Sodium reacts vigorously with water.
(i) Write an equation, with state symbols, for the reaction of sodium with water.
(ii) Describe one observation from the reaction in (i).
(iii) Sketch, on the axes below, an energy profile for this reaction. Label the activation energy, Ea, and the enthalpy change, ΔH.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz CKE i punktacja
Odpowiedź z klucza
(i) 2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g)
balanced equation with correct formulas ✔
correct state symbols ✔
(ii) Any one of:
the solution becomes warm ✔
sodium floats / moves on the surface / melts into a ball / disappears ✔
bubbles of gas / hydrogen / effervescence / fizzing ✔
(iii) exothermic profile: products at a lower energy than the reactants, with a single peak between them ✔
Ea shown as an arrow from the reactants up to the peak AND ΔH shown as an arrow between the levels of reactants and products «pointing down» ✔
Schemat punktowania
(i) [2] award [1] for the balanced equation and [1] for the state symbols. (ii) [1] any one observation. (iii) [2] M1 products lower than reactants, with a peak; M2 Ea and ΔH correctly labelled; Ea must start at the reactant level.