Enthalpy, pH and kinetics experiments — practice questions

Question 1 · difficulty L2 · understanding

In a simple calorimetry experiment, why is the container insulated as well as practical?

• A. To reduce heat exchange with the surroundings
• B. To increase the number of moles reacting
• C. To make the reaction chemically reversible
• D. To force the thermometer to read exactly 0 °C

Question 2 · difficulty L3 · application

A reaction releases heat, but substantial heat escapes to the surroundings before the maximum temperature is recorded. How is the measured temperature rise affected?

• A. It is larger than the ideal temperature rise
• B. It is smaller than the ideal temperature rise
• C. It is unaffected because heat loss changes only pressure
• D. It must become negative for every exothermic reaction

Question 3 · difficulty L3 · application

In a kinetics experiment, the same visible endpoint is reached in 20 s in one run and 40 s in another. Using 1/time as a rate measure, how do the rates compare?

• A. Both runs have the same rate
• B. The 40 s run is twice as fast
• C. The 20 s run is twice as fast
• D. The 20 s run is four times as fast

Question 4 · difficulty L5 · analysis

A student estimates pH using universal indicator and reports 7.43. What is the main problem with this result?

• A. Only acidic solutions can be tested with indicators
• B. Universal indicator cannot be used near neutral pH
• C. A pH value may never contain a decimal
• D. Universal indicator gives approximate pH values