How in the bomb calorimeter the water is recondensed?

In summary, the bomb calorimeter was used to measure the heat of vaporization and the water recondensed was vaporized again.
  • #1
Elz
12
0
1. In the bomb calorimeter used for the test the water is recondensed after it is vaporized

In the bomb calorimeter we measure the HHV as the steam formed there is condensed. What I want to know is how the steam is re condensed? In the wikipedia it says In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a weighed mass of a sample (typically 1-1.5 g) and a small fixed amount of water (to saturate the internal atmosphere, thus ensuring that all water produced is liquid, and removing the need to include enthalpy of vaporization in calculations), is submerged under a known volume of water
...
http://en.wikipedia.org/wiki/Calorimeter#Bomb_calorimeters

If a small amount of water is admitted into the bomb then how it is condensing the steam? Also Bomb calorimeter is called a constant volume calorimeter, What does this constant volume mean? As the bomb calorimeter has to withstand high pressure so what does this constant volume refer to?

Please help me with this.
 
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  • #2
Any additional steam would increase the humidity above 100%, therefore it condenses (unless the temperature increases significantly).
What does this constant volume mean?
What is unclear about constant volume? The whole setup has a fixed volume, it cannot expand or emit any stuff.
As the bomb calorimeter has to withstand high pressure
That is a side-effect of the constant volume: The pressure can be high.
 
  • #3
mfb said:
Any additional steam would increase the humidity above 100%, therefore it condenses (unless the temperature increases significantly).

Additional steam?
I also found in a report that introducing pure oxygen to the bomb would increase the pressure in an isochoric chamber, thus ensuring that the water would be liquid. Can you please explain how it works? I mean i just want to be clear about the mechanism.

What is unclear about constant volume?

Why it is done in constant volume?

Thanks for you response.
 
  • #4
I also found in a report that introducing pure oxygen to the bomb would increase the pressure in an isochoric chamber, thus ensuring that the water would be liquid. Can you please explain how it works? I mean i just want to be clear about the mechanism.
A high pressure increases the boiling point.
Why it is done in constant volume?
The scientist wanted to study something at constant volume, I think. Why? That depends on the experiment.
 
  • #5
Well, it is a bomb calorimeter.

If the reaction didn't occur at constant volume, that would imply that the bomb spread itself all over the lab.
 

1. How does a bomb calorimeter work?

A bomb calorimeter is a device used to measure the heat of combustion of a substance. It consists of a sealed container, or "bomb", where the substance is burned, surrounded by a known amount of water. The heat from the combustion causes the water to increase in temperature, and by measuring the change in temperature, the heat of combustion can be calculated.

2. Why is it important for the bomb calorimeter to be sealed?

The bomb calorimeter must be completely sealed to prevent any heat from escaping during the combustion reaction. This ensures that all of the heat produced by the reaction is transferred to the water, allowing for an accurate measurement of the heat of combustion.

3. How is the water recondensed after the combustion reaction?

After the combustion reaction, the bomb calorimeter is allowed to cool down. As the temperature decreases, the water vapor inside the bomb condenses back into liquid form. This process is known as recondensation.

4. What is the purpose of the water in the bomb calorimeter?

The water in the bomb calorimeter acts as a heat sink, absorbing all of the heat produced by the combustion reaction. By measuring the change in temperature of the water, the heat of combustion can be calculated.

5. Can the bomb calorimeter be used to measure the heat of reactions other than combustion?

While the bomb calorimeter is primarily used to measure the heat of combustion, it can also be used to measure the heat of other reactions, such as neutralization or dissolution. However, the setup and calculations may differ from those used for combustion reactions.

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