Question

A bomb calorimeter with a heat capacity of 30 J/C contains 1000 g of water with an initial temperature of 25°C. A 0.5 g sample of a candy bar is placed in a bomb calorimeter and ignited, resulting in a new water temperature of 30°C. What is ΔE for this reaction?

Answer 1

The energy change (ΔE) for the reaction in the bomb calorimeter is -150 joules, calculated using the formula ΔE = -C×ΔT, with the calorimeter's heat capacity of 30 J/°C and a temperature change of 5°C.

Step-by-step explanation:

The student has asked, "What is ΔE for this reaction?" referring to the change in energy when a 0.5 g sample of a candy bar is burned in a bomb calorimeter, causing the water temperature to increase from 25°C to 30°C. To calculate the change in energy, we use the formula ΔE = -C×ΔT, where C is the heat capacity of the calorimeter, and ΔT is the change in temperature.

Given that the heat capacity of the calorimeter is 30 J/°C and the change in temperature (ΔT) is 5°C (from 25°C to 30°C), we can calculate the energy change as follows:

ΔE = -C×ΔT
ΔE = -(30 J/°C) × (30°C - 25°C)
ΔE = -(30 J/°C) × (5°C)
ΔE = -150 J

Therefore, the energy change (ΔE) for the combustion of the candy bar sample in the bomb calorimeter is -150 joules.