Explain the experiment to determine the internal energy change of a chemical reaction.

Explanation

Internal energy (U): "The total energy stored in the substance at constant temperature and pressure is called its internal energy (U)".
It is state function and is an extensive property
Internal energy change `(triangleU)` is considered as the difference the internal energies of products and reactants.
`triangleU=(U_(p)-U_(f))`
In any path taken (Q-W) is equal to `triangleU`
Where Q=heat and W=work.
The technique of measuring heats of reactions is called calorimetres. The apparatus used is calorimeter.
Calorimeter is a vessel properly insulated and contains water as the calorimetric liquids
A combustioble substance is burnt in oxygen.
Heat evolved during the reaction is measured from the rise in temperature.
Here there is no worke done as `triangleV= 0`
By the raise of temperature of water bath and calorimeter the amount of heat evolved can be determined.
Internal Energy `triangleU=Q. trianglet xx (M)/m " Q=heat capacity"`
`trianglet=t_(2)-t_(1)`
M=Molar mass of substance
m=mass of the substance