Question

A 8.00g sample of substance (substance, molar mass = 152.0 g/mol) was combusted in a bomb calorimeter with a heat capacity of 6.21 kJ/°C. If the temperature rose from 25.0°C to 75.0°C, determine the value of ΔH°comb for substance.

Answer 1

ΔH°comb=-5899.5 kJ/mol

Step-by-step explanation:

First, consider the energy balance:

`m_(c) *Cp*(T_(2)-T_(1))=-n_(s) *H_(c)` Where
`m_(c)` is the calorimeter mass and
`n_(s)` is the number of moles of the samples;
`H_(c)` is the combustion enthalpy. The energy balance says that the energy that the reaction release is employed in rise the temperature of the calorimeter, which is designed to be adiabatic, so it is suppose that the total energy is employed rising the calorimeter temperature.

The product
`m_(c) *Cp` is the heat capacity, so the balance equation is:

`6.21(kJ)/(K)*(75-25)=-8.00g*(mol)/(152.0g)*H_(c)`

So, the enthalpy of combustion can be calculated:

`H_(c)=-5899.5(kJ)/(mol)`

I will be happy to solve any doubt you have.