Question

A 2.49 g sample of aniline (C6H5NH2, molar mass = 93.13 g/mol) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/°C. If the temperature rose from 29.5°C to 69.8°C, determine the value of ΔH°comb for aniline.

Answer 1

The value of delta H° for aniline = 6415 Kj/mol

calculation

Step 1: find heat

Q (heat)  =  C (specific heat capacity)  x ΔT (change in temperature)

C= 4.25 kj/c°

ΔT = 69.8-29.5  = 40.3 c°

Q= 4.25 kj/c  x  40.3 c = 171.28 kj

Step 2:  find the moles of aniline

moles  = mass/molar  mass

= 2.49 g/ 93.13 g/mol =0.0267 moles

Step 3:  find delta H

171.28 kj/0.0267 mol = 6415 kj/mol

since the reaction is  exothermic  delta H = 6415 Kj/mol