Zadanie 2a
Wzorowane na: Chemistry HL Paper 3, November 2024, pytanie 2(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 2a-2c.
The formula of an iron oxide can be found by reducing a weighed sample of the oxide to iron metal in a stream of hydrogen gas, H2. The empty reduction tube is weighed before the sample is added. The apparatus is shown.
Polecenie
Suggest why it is important that hydrogen gas flows through the tube
(i) before heating begins,
(ii) from the end of heating until the product has cooled.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) air/oxygen must be displaced from the tube «so that a mixture of hydrogen and air cannot explode/ignite when heated» ✔
(ii) the hot iron would react with oxygen from the air «and be oxidized again» ✔
Schemat punktowania
One mark per sub-part. (i) Accept 'avoid explosion/combustion of hydrogen' or 'only hydrogen must be present in the tube'. (ii) Accept 'prevent oxidation of the product' or 'ensure the reduction is complete'.