Enthalpy and Calorimetry

Enthalpy is the name for all the energy stored in chemical bonds. This energy increases or decreases during chemical reactions, depending on what kind of reaction it is.

The symbol for Enthalpy is H  and the units are in Joules (J)

There are two different kinds of reactions

Exothermic, which produce energy:


and Endothermic which absorb energy:




These two graphs show what happens to the products in each situation and what happens as the level of enthalpy changes.

In order to use these graphs, we need to get into Calorimetry.

To find out the amount of heat released we need to know 3 things

1. Temperature change (^T) in degrees Celcius
2. Mass (m) in grams
3. Specific heat capacity (C)

Once we know these, using the formula

^H=mC^T

we can figure out the change in Enthalpy!!

For example:

500g of water is heated up on a stove from 10* to 100*. The Specific heat capacity of water is C= 4.18

What is the change in Enthalpy (^H)?

^H=mC^T
^H=(500g)(4.18)(90*)
^H= 188100 J

And there you have it!!

Enthalpy and Calorimetry!!!!!!!!