Zadanie 2b
Wzorowane na: Chemistry HL Paper 3, May 2024, TZ1, pytanie 2(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 2a-2c.
Figure 3 shows how the mass changes when 8.20 g of crystals of hydrated magnesium sulfate are heated from 20 °C to 400 °C. Only water vapour is lost during this process, and no further water vapour is lost above 400 °C.
Polecenie
The uncertainty in each mass reading is ±0.04 g.
(i) Calculate the percentage uncertainty in the total mass loss.
(ii) Using your answer to (i), calculate the absolute uncertainty in the number of moles of water per mole of MgSO4, that is the uncertainty in the 7, to two significant figures.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(i) two readings contribute 0.04 + 0.04 = 0.08 g to the uncertainty in the mass lost ✔
✔
(ii) the requested estimate is 7 × 0.0190 = 0.13 to two significant figures ✔
Schemat punktowania
(i) M1: add both absolute uncertainties; M2: divide by the measured mass loss and convert to a percentage. Award [2] for 1.9% or 1.90%. (ii) Award [1] for 0.13, with two significant figures; ECF from (i).