Unit 8: Acids & Bases
Chemistry · Unit 8 · Paper 1

Acids & Bases unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 20 terms and is the same for everyone, so a teacher can assign “Unit 8, Paper 1” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 37 min 34 points0/17 attempted
1

Titration curve of a weak acid

2

Structure and acid strength

3

pH, pOH and their relationship

4

Henderson-Hasselbalch equation

5

Choosing an indicator

6

Salt hydrolysis

7

Diluting a buffer

8

Why pH = pKa at half-equivalence

9

Autoionization of water

10

Buffer

11

Amphoteric species

12

Strong vs weak acids

Short answer 1. Define or explain: Equivalence point pH

3 pts

Short answer 2. Define or explain: Percent ionization

3 pts

Short answer 3. Define or explain: Relationship of Ka and Kb

3 pts

Short answer 4. Define or explain: Titration curve features to label

3 pts

Free response

10 pts

A student titrates 25.00 mL of a solution of an unknown monoprotic weak acid HA with 0.150 M NaOH. The equivalence point occurs after 32.00 mL of titrant has been added. When 16.00 mL of NaOH has been added, the measured pH is 4.65.

Calculate the moles of HA originally present and its initial molarity.

Determine the Ka of HA, and explain why the pH at 16.00 mL gives this information directly.

Predict whether the pH at the equivalence point is above, below, or equal to 7.00, and justify your answer with a chemical equation.

Explain which of phenolphthalein (transition range 8.3–10.0) or methyl red (transition range 4.4–6.2) is the better indicator for this titration.

Describe the effect on the calculated molarity of HA if the student had rinsed the burette with distilled water and left it wet before filling it with NaOH.