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The label on a packet of dry biscuits gives the following nutritional information - VCE - SSCE Chemistry - Question 9 - 2004 - Paper 1
Question 9
The label on a packet of dry biscuits gives the following nutritional information. serving size 35 g protein 3.7 g fat - saturated 0.80 g - unsaturated 0.10 g carb... show full transcript
Worked Solution & Example Answer:The label on a packet of dry biscuits gives the following nutritional information - VCE - SSCE Chemistry - Question 9 - 2004 - Paper 1
Step 1
i. Calculate the total possible energy available to the body per gram of biscuit.
Answer
To calculate the total possible energy, we need to determine the energy contributions from protein, fat, and carbohydrates. Using the given energy available per gram:
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Calculate the energy from protein:
ext{Energy from protein} = 3.7 ext{ g (protein)} imes 16 ext{ kJ/g} = 59.2 ext{ kJ}
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Calculate the energy from fat:
ext{Total fat} = 0.80 ext{ g (saturated)} + 0.10 ext{ g (unsaturated)} = 0.90 ext{ g}
ext{Energy from fat} = 0.90 ext{ g} imes 37 ext{ kJ/g} = 33.3 ext{ kJ}
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Calculate the energy from digestible carbohydrates:
ext{Energy from carbohydrates} = 26.0 ext{ g (carbohydrates)} imes 17 ext{ kJ/g} = 442.0 ext{ kJ}
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Add all the energy contributions together:
ext{Total energy} = 59.2 ext{ kJ (from protein)} + 33.3 ext{ kJ (from fat)} + 442.0 ext{ kJ (from carbohydrates)} = 534.5 ext{ kJ}
Thus, the total possible energy available to the body per gram of biscuit is approximately 534.5 kJ.
Step 2
ii. Give a possible explanation for the difference between this value and that calculated in part i.
Answer
The discrepancy in energy values arises from factors such as:
- Incomplete combustion: The bomb calorimeter measures the energy released during combustion. If the biscuit does not combust completely, the energy recorded will be lower than the theoretical energy calculated from nutritional information.
- Cellulose fiber: The energy available from cellulose fiber may not be fully utilized during digestion. The calorimeter does not account for the energy that cannot be digested or metabolized by the body.
- Measurement error: There can exist measurement errors in calorimeter readings or in the sample used for determining energy values, which can affect the results.
Therefore, when calculating energy, it's crucial to consider these factors that influence the total energy release during consumption.