A 2.5 g sample of french fries is placed in a calorimeter with 500.0 g of water at an initial temperature of 21 °C. After combustion of the french fries, the water has a temperature of 48 °C. What is the caloric value (kcal/g) of the french fries?
A) 11 kcal/g
B) 5.4 kcal/g
C) 0.14 kcal/g
D) 4.2 kcal/g
E) 14 kcal/g

Question

A 2.5 g sample of french fries is placed in a calorimeter with 500.0 g of water at an initial temperature of 21 °C. After combustion of the french fries, the water has a temperature of 48 °C. What is the caloric value (kcal/g) of the french fries? 
A) 11 kcal/g 
B) 5.4 kcal/g 
C) 0.14 kcal/g 
D) 4.2 kcal/g 
E) 14 kcal/g

Quizplus · Accepted Answer

First, calculate the energy absorbed by the water using the formula $q = mc\Delta T$, where $m$ is the mass of the water (500.0 g), $c$ is the specific heat capacity of water (1.00 cal/g°C), and $\Delta T$ is the change in temperature (48 °C - 21 °C = 27 °C). Thus, $q = 500.0 \times 1.00 \times 27 = 13500$ cal. Since 1 kcal = 1000 cal, the energy absorbed by the water is 13.5 kcal. To find the caloric value per gram of the french fries, divide the total energy by the mass of the french fries: $13.5 \text{ kcal} / 2.5 \text{ g} = 5.4 \text{ kcal/g}$.

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