Question

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

Answer 1

To answer the question above, we need to convert 12.8 g to moles by dividing by 46.07 first.

For every mole you burn, you get 1235 kJ of heat. So multiply your number of moles by 1235. It'll be something in the neighborhood of 500. 

Take your kJ that you calculated and divide by 5.65 to get the number of degrees that your calorimeter goes up. Add that to 25.

I hope my answer helped you

Answer 2

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.