Find the ΔE of the combustion of octane in a bomb calorimeter

The correct answer is -5506.3 KJ/mol.In summary, the conversation discusses the combustion of octane in a bomb calorimeter in the presence of water. The heat capacity of the bomb calorimeter and water are given, and the goal is to find the change in energy of the reaction. The correct answer is found by calculating the heat of the water and calorimeter separately, and then adding them together. The textbook's method involves using only the heat of the calorimeter.
  • #1
MarcL
170
2

Homework Statement



Consider the combustion of octane that is burned in a bomb calorimter in the presence of 10.00kg of water. When burning 8.10mL of octane (.703g/ml=d) the temp. of the surrounding water increase by 5.66°C. The heat capacity of the bomb calorimter is 6.656Kj/ °C and the water is 4.184 j/g x °C

Homework Equations



q=mcΔT
qcal=Ccal x ΔT
ΔErxn= qrxn / moles of octane

The Attempt at a Solution



find Q of water which gave me 236.8 KJ by q=mcΔT ( m = 10000KG )
and find Q cal which ended up to 37.13 KJ by q=Ccal ΔT
then I added both Heat to get 273.9 Kj and then I divided by the number of mole found which was .049852045 moles.

However I got as an answer -5494.25 and the answer is -5506.3 Kj/mol

P.s: why does my textbook says to just use the Q of the calorimter and not add it up to the one of water in order to find the ΔE?
 
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  • #2
Check your arithmetic.
 

FAQ: Find the ΔE of the combustion of octane in a bomb calorimeter

What is the purpose of finding the ΔE of the combustion of octane in a bomb calorimeter?

The purpose of finding the ΔE (change in energy) of the combustion of octane in a bomb calorimeter is to determine the amount of energy released when octane is burned. This information is useful for understanding the chemical properties of octane and can be used in various fields such as energy production and environmental studies.

How is the ΔE calculated using a bomb calorimeter?

The ΔE is calculated by measuring the change in temperature of the water in the bomb calorimeter before and after the combustion of octane. The heat capacity of the calorimeter must also be taken into account. The equation used to calculate ΔE is: ΔE = q / mC, where q is the heat released, m is the mass of the substance burned, and C is the heat capacity of the calorimeter.

What is the significance of using a bomb calorimeter in this experiment?

A bomb calorimeter is used in this experiment because it allows for the measurement of the heat released during a combustion reaction at constant volume. This is important because it eliminates the effects of pressure changes and ensures that all of the energy released is contained within the system.

How does the ΔE of octane differ from other hydrocarbons?

The ΔE of octane can vary from other hydrocarbons due to differences in their molecular structures. For example, longer chain hydrocarbons tend to have higher ΔE values because they have more bonds to break during combustion. Additionally, the presence of double or triple bonds in a molecule can affect the amount of energy released during combustion.

How is the ΔE of octane in a bomb calorimeter related to its calorific value?

The ΔE of octane in a bomb calorimeter is directly related to its calorific value, which is the amount of energy released per unit mass of octane during combustion. The calorific value can be calculated by dividing the ΔE by the mass of octane burned. This information is useful for comparing the energy content of different fuels and determining their efficiency for energy production.

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