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The following table contains information about three experiments - VCE - SSCE Chemistry - Question 9 - 2009 - Paper 1
Question 9
The following table contains information about three experiments. In each experiment 0.10 mol of an alkane is burned completely and all the energy released is used t... show full transcript
Worked Solution & Example Answer:The following table contains information about three experiments - VCE - SSCE Chemistry - Question 9 - 2009 - Paper 1
Step 1
I. Calculate the energy released from combustion
Answer
The energy released during combustion can be determined using the data available for each alkane. The heat of combustion values are:
- Butane: approximately 2860 kJ/mol
- Pentane: approximately 3516 kJ/mol
- Hexane: approximately 4163 kJ/mol
For each experiment, the total energy available from 0.10 mol of each alkane can be found by multiplying the moles by the heat of combustion:
- Butane: kJ
- Pentane: kJ
- Hexane: kJ
Step 2
II. Determine the energy required to heat water
Answer
The energy required to heat 1.00 L of water from 20°C to its boiling point (100°C) can be calculated using the formula:
Where:
- = mass of water (1 kg for 1 L)
- = specific heat capacity of water (approximately 4.18 kJ/kg°C)
- = change in temperature (100°C - 20°C = 80°C)
Thus, the energy required:
Step 3
III. Compare the energy released versus energy required
Answer
Now, comparing the energy released in each experiment with the energy required to heat the water:
- Experiment I (Butane): 286.0 kJ < 334.4 kJ (not sufficient)
- Experiment II (Pentane): 351.6 kJ > 334.4 kJ (sufficient)
- Experiment III (Hexane): 416.3 kJ > 334.4 kJ (sufficient)
Thus, the water will be heated to its boiling temperature in experiments II and III.