## anonymous 4 years ago Some ethane (C2H6) was burned in a bomb calorimeter. If 31.999g of oxygen was burned with the ethane and the temperature of the calorimeter rose by 30deg C, calculate the molar heat of combustion of C2H6. The mass of the calorimeter was 2.0kg and had a specific heat capacity of 0.39kJ/kg degC

1. anonymous

Since there is water in the bomb calorimeter, dont you have to do q=mct to the water?? why the solution only shows q= (2kg) (0.39) (30) , which is only the bomb calorimeter itself but not water

2. anonymous

We typically include water in the equation when we are finding the heat released or absorbed of reactions occurring in aqueos solution. In this, the reaction occurs in air. The bomb calorimeter simply creates an adiabatic environment so we can accurately measure the enthalpy associated with the reaction.

3. anonymous

how do you it occurs in the air though?? is it because the question didnt mention about water?

4. anonymous

What is the question asking for first of all?

5. anonymous

Methane (a gas) reacts with oxygen (a gas). Combustion processes don't very well occur in water.

6. anonymous

ohhh, ok i get it now, thanks eashmore :)

7. anonymous

and to rogue, it is asking for the molar heat of combustion of C2H6"

8. anonymous

$2C_2H_6 + 7O_2 \rightarrow 4CO_2 + 6H_2O$

9. anonymous

Alright, thats easy than, you can calculate the energy released for 2/7th mole of C2H6 using the numbers they give you. Then just multiply it by 3.5 to get the molar heat of combustion of C2H6

10. anonymous

thank you both for your help :D