Energy changes
Read our general notes on Risk Assessment
How do you work out the standard enthalpy change of formation?
Ulex replies ... Begin by writing the equation for the formation of the substance concerned from its elements
C(s) + 2H2(g) -> CH4(g)
You want the enthalpy change for this reaction.
Next, think out what you can do to the substances on both sides of the equation which will result in the same products. In this case, the simplest thing is to burn them. It is possible to do all the combustion reactions in a calorimeter and to measure the enthalpy changes.
Set up a Hess triangle with the equation above and with the combustion products at the third point of the triangle. Solve this triangle to get the required enthalpy change.
Risk assessment
Before attempting any practical work based on the advice and suggestions on this website, you must do the following. Identify any hazards, assess the risks from these hazards, and then decide appropriate control measures to reduce the risks. You must have these approved by those in authority in your school or college laboratory. Do not rely on what is said on this website.
For further guidance see our tutorial on Risk Assessment.
Rate this page or react
Share your views on this page, 12 ratings so far
, rated at 
updated: 02 March 2004
