pH and redox quiz: acids, bases, buffers and cells.
Test in ItalianThe questions of this simulator are in Italian, as in the real exam.
15 questions in 40 minutes, no penalty for wrong answers: pH and pOH, strong and weak acids, buffers, titrations, oxidation numbers, balancing redox equations and standard potentials, with the calculations marked. The correct answer to every question and your weak topics arrive by email for free; with an account you see them straight away here, together with the score, which is already on the page for everyone. The guided step-by-step solution unlocks with your first lesson.
A free high-school chemistry quiz on pH and redox reactions, the two topics of the Year 4 chemistry test in February.
| Topic | What it covers |
|---|---|
| pH and strong acids/bases | logarithms, pOH, dilutions, diprotic electrolytes |
| Weak acids | dissociation constant, comparison with strong acids |
| Buffers | Henderson–Hasselbalch, choosing the conjugate acid-base pair |
| Neutralisation and titrations | equivalence, excess acid or base, final pH |
| Oxidation number | rules, polyatomic ions, exceptions such as peroxides |
| Redox and cells | oxidising and reducing agents, electrons exchanged, e.m.f. and spontaneity |
15 questions drawn at random from a bank of 49 · 40 minutes · no penalty (blank = wrong = 0 points) · options shuffled on every attempt. Original questions, recalculated one by one.
Two worked examples from the test
Una soluzione acquosa a 25 °C ha mol/L. Qual è il suo pH?
Solution
Il pH è il logaritmo decimale cambiato di segno della concentrazione di ioni idrogeno.
Il valore 9,0 è il pOH (14 − 5), non il pH; il segno meno va applicato dopo il logaritmo, non prima.
Una soluzione ha mol/L. Quanto vale il pH? (Si usi )
Solution
Si scompone la concentrazione in un prodotto di potenze:
Il pH deve essere compreso tra 3 e 4 perché è compresa tra e : l'opzione 4,30 deriva da un errore di segno sul termine e cadrebbe fuori dall'intervallo.
In the online practice test you will find 13 more questions like these; the correct answer to every question arrives by email.
Where you lose marks in a pH and redox test.
The February chemistry test in Year 4 puts together two chapters that seem far apart: acid-base equilibrium, which is all logarithms and concentrations, and redox reactions, which are all electron bookkeeping. What they share is that mistakes are rarely down to not knowing the theory and often down to a step taken for granted: a minus sign in front of the logarithm, a forgotten factor of 2, a half-reaction balanced halfway.
With pH there are three recurring mistakes. The first is the sign: pH is minus the logarithm, and a concentration of 10⁻⁵ mol/L does not have a pH of −5. The second is the factor of 2 for diprotic acids and bases: sulfuric acid and barium hydroxide release two ions per formula unit, and without the 2 the pH is off by 0.3 units. The third is treating a weak acid like a strong one: the concentration of H⁺ is the square root of Ka · C, not the concentration of the acid.
With redox, almost everything is decided before you write the coefficients, when you assign the oxidation numbers: in hydrogen peroxide oxygen is not −2, and in the ammonium ion the sum gives the charge, not zero. Finally, in cells the sign of the e.m.f. decides spontaneity and is obtained by subtracting the anode potential from the cathode potential, never by adding them.
To revise the theory: the guide to acids, bases and pH for Year 4.
Frequently asked questions.
Do I need to know logarithms by heart?
No: questions that need a logarithm that is not a round number (for example log 2 or log 3) give it in the text, and the others use concentrations that are powers of ten.
Do I have to know the standard potentials by heart?
No. In the questions on cells the potentials you need are always written in the text, as in a well-made class test: what is assessed is whether you can use them, not whether you remember them.
Does the quiz also cover solubility equilibria?
No. The quiz covers pH, buffers, titrations, oxidation numbers, balancing redox equations and cells; solubility products are not included.
Can I retake the quiz?
Yes. On every attempt 15 different questions are drawn from a larger bank and the options change order, so a second attempt really tells you how much you have learned.
What do I see at the end of the practice test?
The correct answer to every question and your weak topics arrive by email for free; with an account you see them straight away here, together with the score, which is already on the page for everyone. The guided step-by-step solution unlocks with your first lesson.
Do pH and redox seem like two different subjects?
The quiz separates calculation errors from set-up errors. In lessons we work on the topic where you lose the most marks, with graded exercises and timed tests.