A 12.8 g sample of ethanol (C2H5OH) is burned in a bomb calorimeter with a heat capacity of 5.65 kJ/°C. 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.

delta H rxn = -1235

C2H5OH + 3O2 -> 2CO2 +3H2O

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Larus Larus · Answer 1 · 2019-03-06T19:42:12-05:00

The final temperature of the calorimeter is 85.71 degree C.

Heat of the reaction is -1235 kJ/mol

Heat discharged at the time of reaction is 1235 kJ/mol

The moles of ethanol are calculated by using the formula mass of ethanol / molar mass of ethanol

= 12.8 g / 46 g/mol = 0.278 moles

Thus, the no. of moles of ethanol is 0.278 moles

The heat released when ethanol is combusted is:

0.278 moles × 1235 kJ/mol = 343 kJ

The final temperature is determined as,

343 kJ = (heat capacity) (temperature difference)

343 kJ = 5.65 (T - 25)

T-25 = 343 / 5.65

T-25 = 60.71

T = 85.71 degree C

Thus, the final temperature is 85.71 degree C.

pstnonsonjoku pstnonsonjoku · Answer 2 · 2021-11-03T13:48:45-04:00

The final temperature of the system is 85.8°C.

We have the following information from the question;

Mass of ethanol = 12.8 g

Molar mass of ethanol= 46.07 g/mol

Heat of reaction= -1235 KJ/mol

Number of moles = 12.8 g/46.07 g/mol = 0.278 moles

Heat absorbed by calorimeter = number of moles × Heat of reaction =

0.278 moles × -1235 KJ/mol = -343.33 KJ

Given that;

Energy absorbed by the calorimeter = heat capacity × temperature rise

343.33 = 5.65 × (T2 - 25)

343.33 = 5.65T2 - 141.25

343.33 + 141.25 = 5.65T2

T2 = 343.33 + 141.25/5.65

T2 = 85.8°C

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