Zacznij za darmoZacznij

Zadanie 1a

5 pktotwarteśrednie (szac.)Paper 1B, maj 2026, TZ3

Wzorowane na: Chemistry SL Paper 1B, May 2026, TZ3, pytanie 1(a). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.

Zapisz zadanie

Darmowe konto pozwoli wrócić do niego później.

Informacja do zadań 1a-1c.

A student investigated the reaction between aqueous nitric acid, HNO3, and solid magnesium carbonate, MgCO3, using two different methods to follow its rate.

In Method 1, a conical flask containing the aqueous acid stood on a balance and the mass reading was recorded at regular intervals while the gas escaped from the open flask. In Method 2, the flask was closed with a stopper carrying a delivery tube; the gas passed through the tube into an inverted measuring cylinder filled with water and standing in a trough of water, and the volume of gas collected was recorded at regular intervals.

apparatus for Method 1 (conical flask on a balance reading 0.00 g) and Method 2 (stoppered flask with a delivery tube leading to an inverted measuring cylinder in a trough of water)

Polecenie

(i) Write a balanced equation for the reaction, including state symbols.

(ii) Deduce what property of this reaction makes it possible to follow its rate by both methods.

(iii) Magnesium carbonate was used in excess so that all of the acid would react. Calculate the minimum mass of MgCO3, in g, that is needed to react completely with 25.0 cm3 of 0.20 mol dm−3 HNO3. Use section 7 of the data booklet.

Sprawdź rozwiązanieUkryj rozwiązanieKlucz CKE i punktacja

Zanim porównasz z kluczem

Jak poszło Ci z tym zadaniem?

Wybierz ocenę: zapisze wynik i od razu oznaczy zadanie jako zrobione.

ŁatweŚrednieTrudne

Zapis wymaga darmowego konta. Załóż konto

Odpowiedź z klucza

(i) MgCO3(s) + 2 HNO3(aq) → Mg(NO3)2(aq) + H2O(l) + CO2(g) «correct species and balancing» ✔

correct state symbols ✔

OR

MgCO3(s) + 2 H+(aq) → Mg2+(aq) + H2O(l) + CO2(g) «ionic equation, acceptable for both marks»

(ii) a gas / carbon dioxide is released «from the reaction mixture» ✔

(iii) n(HNO3) = «0.0250 × 0.20 =» 5.0 × 10−3 «mol» ✔

«n(MgCOX3)=12×5.0×10−3=2.5×10−3n(\ce{MgCO3}) = \frac{1}{2} \times 5.0 \times 10^{-3} = 2.5 \times 10^{-3} mol; M(MgCO3) = 24.31 + 12.01 + 3(16.00) = 84.32 g mol−1»

m(MgCO3) = «2.5 × 10⁻³ × 84.32 =» 0.21 «g» ✔

Schemat punktowania

(i) [2]: M1 correct formulae and balancing (accept the ionic equation); do not award M1 for H2CO3 as a product. M2 correct state symbols. (ii) [1] for release or formation of a gas / carbon dioxide; accept loss of mass AND release of gas. (iii) [2]: M1 amount of acid 5.0 × 10⁻³ mol; M2 mass of carbonate from the 1 : 2 mole ratio. Award [2] for the correct final answer. Award [1] for 0.42 g, which comes from using a 1 : 1 ratio.

Komentarz

The mole ratio of carbonate to acid is read from the balanced equation in (i): one mole of MgCO3 reacts with two moles of acid.

Umiejętności w zadaniu