Wzorowane na: Chemistry SL Paper 1B, May 2025, TZ3, pytanie 1(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Informacja do zadań 1a-1e.
Nitrogen dioxide,
(i) Suggest, giving a reason for each, two different safety precautions that should be taken when carrying out either of these preparations.
(ii) Deduce the coefficients needed to balance the following equation for the reaction of silver with concentrated nitric acid.
(iii) Calculate the mass, in g, of nitric acid, , consumed when 0.0150 mol of
(i) Any two of:
safety goggles/eye protection AND the acid is corrosive / the gas can damage the eyes ✔
fume cupboard/fume hood AND is toxic / must not be inhaled ✔
tongs/heat-resistant gloves AND to prevent burns from the hot apparatus or from the acid ✔
(ii) ✔
(iii) «from (ii),
(i) [2 max]: one mark for each precaution paired with a matching reason; award [1 max] if two precautions or two reasons are given without pairing. General laboratory rules (lab coat, tied-back hair, 'a well-ventilated room') and 'gas mask' do not score. (ii) [1] for the coefficients 1, 2, 1, 1, 1 or any correct multiple. (iii) [1] for 1.89 g; ECF for a mass consistent with the student's own equation in (ii) (0.945 g from a 1 : 1 ratio scores only with ECF).
The mole ratio of metal to NO2 must be read from the balanced equation in (ii); here it is 1 : 1, so no halving is needed.
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