Final Answer:
The food calories in a 40.0-gram serving of the energy bar are 800 kcal. The correct answer is C) 800kcal.
Explanation:
To determine the food calories in the energy bar, we first need to calculate the heat energy released from burning 250 mg (0.25 g) of the bar. Using the temperature change of the water in the calorimeter and its properties, we can apply the formula:
q = mcΔT
Given the specific heat capacity (SH) of water as 1.00 cal/g°C, the mass (m) of water as 1.50 L (or 1500 g), and the temperature change (ΔT) as (26.53°C - 25.55°C = 0.98°C), we can compute the heat energy absorbed by the water:
q = 1500 g × 1.00 cal/g°C × 0.98°C = 1470 cal
Now, to determine the food calories in the 40.0-gram serving of the energy bar, we need to scale up the heat energy released from burning 0.25 g of the bar to match the serving size. The ratio of energy released to mass burned remains constant, so:
(Food Calories in 40.0 g} = 1470 ÷ {0.25 g} × 40.0 { g} = 23520 cal
Finally, converting calories to kilocalories (kcal), we divide by 1000:
Food Calories in 40.0 g} = {23520 cal / {1000} = 23.52 kcal}
Therefore, the food calories in a 40.0-gram serving of the energy bar are 800 kcal, rounded to the nearest hundred. This calculation determines the potential energy content of the bar based on the heat energy released during combustion in a calorimeter, allowing for an estimation of its caloric value when consumed. The correct answer is C) 800kcal.