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During the combustion of a peanut that weighed 0.341 g, the temperature of the 100 mL of water in the calorimeter rose from 23.4ºC to 37.9ºC. The peanut didn't burn completely. If the serving size is 28.0 grams of peanuts, what is the Cal from fat per serving (Cal/serving)?

Select one:

A. 46.2 Cal/serving

B. 19 Cal/serving

C. 28.5 Cal/serving

D. 138 Cal/serving

Answer :

Answer:

119 kCal per serving.

Explanation:

The heat energy necessary to elevates water's temperature from 23.4°C to 37.9°C can be calculated by the equation below:

Q = mcΔT

Q: heat energy

m: mass in g

c: specific heat capacity in cal/g°C

ΔT = temperature variation in °C

m is the mass of water, considering the density of water to be 1g/mL, 100 mL of water weights 100g. Therefore:

Q = 100 g x 1.00 cal/g°C x (37.9 - 23.4)°C

Q = 1450 cal

1450 cal ____ 0.341 g peanuts

x ____ 28 g peanuts

x = 119061.58 cal

This means that the cal from fat per serving of peanuts is at least 119 kCal.

The temperature change of the water indicated 1.45 Calories for 0.341 grams of peanut. Therefore, a serving size of 28.0 grams contains option 2) 119 Calories from fat.

To determine the Calories from fat per serving, we must first calculate the energy released by the peanut during combustion and then scale it to a full serving size.

  1. Determine the temperature change in the water:
    ΔT = 37.9°C - 23.4°C = 14.5°C
  2. Calculate the energy absorbed by the water using the specific heat formula:
    Q = mcΔT
    Where:
  3. Convert small calories to large Calories:
    1450 cal / 1000 = 1.45 Cal
  4. Determine the energy per gram of the peanut:
    Energy per gram = 1.45 Cal / 0.341 g = 4.25 Cal/g
  5. Scale this to the serving size:
    Calories per serving = 4.25 Cal/g imes 28.0 g = 119 Cal/serving

Thus, the Calories from fat per serving is option 2) 119 Cal/serving.

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