A student does an experiment to determine a value for the enthalpy of combustion of heptane - AQA - A-Level Chemistry - Question 3 - 2021 - Paper 2
Question 3
A student does an experiment to determine a value for the enthalpy of combustion of heptane.
Figure 2 shows some of the apparatus used.
Design a table to record al... show full transcript
Worked Solution & Example Answer:A student does an experiment to determine a value for the enthalpy of combustion of heptane - AQA - A-Level Chemistry - Question 3 - 2021 - Paper 2
Step 1
Design a table to record all the readings necessary to determine an experimental value for the enthalpy of combustion for heptane in this experiment.
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Temperature (°C)
Mass of water (g)
Mass of heptane (g)
Initial Temperature (°C)
Final Temperature (°C)
Step 2
Suggest two disadvantages of using a glass beaker on a tripod and gauze.
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Disadvantage 1: Glass is a poorer conductor than copper, leading to less efficient heat transfer.
Disadvantage 2: A tripod and gauze would elevate the beaker above the flame, which could reduce the heat applied to the substance.
Step 3
Suggest two reasons why the value of enthalpy of combustion from this experiment is less exothermic than a data book value.
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Reason 1: Heat loss to the surroundings or to the copper/calorimeter during the experiment.
Reason 2: Incomplete combustion of heptane, resulting in lower energy release.
Step 4
Suggest one addition to this apparatus that would improve the accuracy of the enthalpy value obtained.
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
