Zadanie 26
Wzorowane na: Chemistry HL Paper 1, May 2024, TZ1, pytanie 26. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Polecenie
At 298 K the pKa of methanoic acid is 3.75 and the pKa of ethanoic acid is 4.76. Which statement is correct for solutions of these acids with the same concentration?
A. Ethanoic acid is a stronger acid than methanoic acid.
B. The methanoate ion is a weaker base than the ethanoate ion.
C. The Ka of methanoic acid is smaller than the Ka of ethanoic acid.
D. The pH of the methanoic acid solution is higher than the pH of the ethanoic acid solution.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
B ✔
«the smaller pKa means a larger Ka, so methanoic acid is the stronger acid and ionizes more, giving the lower pH; since Ka × Kb = Kw, the conjugate base of the stronger acid, the methanoate ion, is the weaker base»
Schemat punktowania
One mark for the correct option.