Zadanie 28
Wzorowane na: Chemistry SL Paper 1, November 2023, TZ2, pytanie 28. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Polecenie
The concentration of ethanoic acid in a sample of vinegar is determined by titration against a solution of sodium hydroxide of known concentration. Which procedure is most likely to produce a systematic error in the calculated concentration of the acid?
A. Rinsing the burette with distilled water but not with sodium hydroxide solution before filling it
B. Carrying out three titrations instead of five
C. Reading the meniscus at slightly different positions each time
D. Swirling the flask at a different speed in each titration
Sprawdź rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
A ✔
«Water left in the burette dilutes the sodium hydroxide solution every time, so every titre is larger than it should be, which is a systematic error; the other procedures introduce random variation or reduce the precision»
Schemat punktowania
One mark for the correct option.