Chem 123 Lab Final UBC Actual Exam
Questions And Answers Practice
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**Q1. Why do we perform iodometric titrations?**
A) To measure the pH of an unknown solution
B) To find the concentration of an unknown by mixing it with a solution
of known concentration
C) To determine the boiling point of a substance
D) To separate mixtures based on solubility
**Answer: B**
**Rationale:** Iodometric titrations are a type of redox titration used
to determine the concentration of an unknown analyte by reacting it
with a standardized solution .
**Q2. What are the four general steps of an iodometric titration?**
A) Measure, mix, heat, cool
B) Combine solutions, reach endpoint, calculate, determine the
concentration of the unknown
C) Weigh, dissolve, filter, evaporate
D) Pipette, dilute, shake, read
**Answer: B**
,**Rationale:** The process involves combining reactants, observing the
endpoint (color change), calculating moles from the known reactant,
and determining the unknown concentration .
**Q3. What reaction takes place during an iodometric titration?**
A) Acid-base neutralization
B) Precipitation reaction
C) Oxidation-reduction reaction
D) Complexation reaction
**Answer: C**
**Rationale:** Iodometric titrations involve the transfer of electrons
between species, specifically the reduction of iodine to iodide or the
oxidation of iodide to iodine .
**Q4. What is used as the oxidizing agent in an iodometric titration?**
A) Sodium thiosulfate
B) Potassium iodate
C) Ascorbic acid
D) Starch
**Answer: B**
**Rationale:** Potassium iodate (KIO3) is a strong oxidizing agent used
to generate iodine in solution for the titration .
,**Q5. A top-loading balance obtains a mass to the nearest:**
A) ± 0.001 g
B) ± 0.01 g
C) ± 0.1 g
D) ± 0.0001 g
**Answer: C**
**Rationale:** Top-loading balances are used for preliminary weighing
and have an uncertainty of ±0.05 g to ±0.1 g .
**Q6. An analytical balance obtains a mass to the nearest:**
A) ± 0.1 g
B) ± 0.01 g
C) ± 0.001 g
D) ± 0.0001 g
**Answer: D**
**Rationale:** Analytical balances are high-precision instruments that
measure to the nearest 0.0001 g (0.1 mg) .
**Q7. Which balance needs to be recorded to 4 decimal places?**
A) Top-loading balance
B) Analytical balance
C) Both A and B
D) Neither A nor B
, **Answer: B**
**Rationale:** Due to its high precision, measurements from an
analytical balance must always be recorded to four decimal places (e.g.,
1.2345 g) .
**Q8. When is a reading considered stable on a balance?**
A) If it persists for 1 second
B) If it persists for 2 seconds
C) If it persists for 5 seconds
D) If it persists for 10 seconds
**Answer: B**
**Rationale:** To ensure an accurate measurement, you should wait
for the display to remain unchanged for approximately 2 seconds
before recording .
**Q9. At what temperature should objects be weighed?**
A) Any temperature is acceptable
B) Room temperature
C) As cold as possible
D) As hot as possible
**Answer: B**
**Rationale:** Hot or cold objects create convection currents that
destabilize the balance reading and cause inaccuracies .
Questions And Answers Practice
Questions with Solutions Newest |
Already Graded A+.
**Q1. Why do we perform iodometric titrations?**
A) To measure the pH of an unknown solution
B) To find the concentration of an unknown by mixing it with a solution
of known concentration
C) To determine the boiling point of a substance
D) To separate mixtures based on solubility
**Answer: B**
**Rationale:** Iodometric titrations are a type of redox titration used
to determine the concentration of an unknown analyte by reacting it
with a standardized solution .
**Q2. What are the four general steps of an iodometric titration?**
A) Measure, mix, heat, cool
B) Combine solutions, reach endpoint, calculate, determine the
concentration of the unknown
C) Weigh, dissolve, filter, evaporate
D) Pipette, dilute, shake, read
**Answer: B**
,**Rationale:** The process involves combining reactants, observing the
endpoint (color change), calculating moles from the known reactant,
and determining the unknown concentration .
**Q3. What reaction takes place during an iodometric titration?**
A) Acid-base neutralization
B) Precipitation reaction
C) Oxidation-reduction reaction
D) Complexation reaction
**Answer: C**
**Rationale:** Iodometric titrations involve the transfer of electrons
between species, specifically the reduction of iodine to iodide or the
oxidation of iodide to iodine .
**Q4. What is used as the oxidizing agent in an iodometric titration?**
A) Sodium thiosulfate
B) Potassium iodate
C) Ascorbic acid
D) Starch
**Answer: B**
**Rationale:** Potassium iodate (KIO3) is a strong oxidizing agent used
to generate iodine in solution for the titration .
,**Q5. A top-loading balance obtains a mass to the nearest:**
A) ± 0.001 g
B) ± 0.01 g
C) ± 0.1 g
D) ± 0.0001 g
**Answer: C**
**Rationale:** Top-loading balances are used for preliminary weighing
and have an uncertainty of ±0.05 g to ±0.1 g .
**Q6. An analytical balance obtains a mass to the nearest:**
A) ± 0.1 g
B) ± 0.01 g
C) ± 0.001 g
D) ± 0.0001 g
**Answer: D**
**Rationale:** Analytical balances are high-precision instruments that
measure to the nearest 0.0001 g (0.1 mg) .
**Q7. Which balance needs to be recorded to 4 decimal places?**
A) Top-loading balance
B) Analytical balance
C) Both A and B
D) Neither A nor B
, **Answer: B**
**Rationale:** Due to its high precision, measurements from an
analytical balance must always be recorded to four decimal places (e.g.,
1.2345 g) .
**Q8. When is a reading considered stable on a balance?**
A) If it persists for 1 second
B) If it persists for 2 seconds
C) If it persists for 5 seconds
D) If it persists for 10 seconds
**Answer: B**
**Rationale:** To ensure an accurate measurement, you should wait
for the display to remain unchanged for approximately 2 seconds
before recording .
**Q9. At what temperature should objects be weighed?**
A) Any temperature is acceptable
B) Room temperature
C) As cold as possible
D) As hot as possible
**Answer: B**
**Rationale:** Hot or cold objects create convection currents that
destabilize the balance reading and cause inaccuracies .
