A 12.8 g sample of ethanol (C₂H₅OH)is burned in a bomb calorimeter with a heat capacity of 5.65 kJ ${ } ^ { \circ } \mathrm { C } ^ { - 1 }$ .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 $\mathrm { mol } ^ { - 1 }$ . C₂H₅OH(l)+ 3O₂(g)? 2CO₂(g)+ 3H₂O(g) $D _ { \mathrm { r } }$ U= -1235 kJ $\mathrm { mol } ^ { - 1 }$

Question

Quizplus · Accepted Answer

First, we need to calculate the amount of heat released from the combustion of ethanol.

n = mass/molar mass = 12.8 g / 46.07 g/mol = 0.278 mol

q = nΔHr = (0.278 mol) (-1235 kJ/mol) = 343.4 kJ

This amount of heat is absorbed by the calorimeter and its surroundings, resulting in a temperature increase.

q = CpΔT

ΔT = q/Cp = (343.4 kJ) / (5.65 kJ/°C) = 60.8 °C

Therefore, the final temperature of the calorimeter is 25.0°C + 60.8°C = 85.8°C, or approximately 85.7°C (rounded to 3 significant figures).

The correct answer is D) 85.7°C.

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