A 12.8 g sample of ethanol (C₂H₅OH)is burned in a bomb calorimeter with a heat capacity of 5.65 kJ °C^-1. Using the information below, determine the final temperature of the calorimeter if the initial temperature is 25.0°C. The molar mass of ethanol is 46.07 g mol^-1. C₂H₅OH(l)+ 3O₂(g)→ 2CO₂(g)+ 3H₂O(g)Δ_rU= -1235 kJ mol^-1

Question

Quizplus · Accepted Answer

First, we need to calculate the amount of heat released by the combustion of ethanol:

n = 12.8 g / 46.07 g mol-1 = 0.2778 mol

q = nΔHr = 0.2778 mol × (-1235 kJ mol-1) = -342.6 kJ

Next, we need to use the heat capacity of the calorimeter to calculate the temperature change:

q = CΔT

ΔT = q / C = (-342.6 kJ) / (5.65 kJ °C-1) = -60.53 °C

Finally, we need to add the temperature change to the initial temperature:

Tf = 25.0 °C - 60.53 °C = 85.7 °C

Therefore, the final temperature of the calorimeter is 85.7 °C (choice D).

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A 128 G Sample of Ethanol (C₂H₅OH)is Burned in a Bomb