Other Conversions: Volume to Heat

Volume at Standard Temperature and Pressure can be found using the conversion factor 22.4 L/mol. Heat can be individually included as a separate term in chemical reactions, known as enthalpy.  There are two distinctions with heat in chemical reactions: 

• Reactions that release heat (Exothermic) 
• Reactions that absorb heat (Endothermic) 

Both of these are seen in stoichiometry. 

Example One: 

If 5.0g of Potassium chlorate decompose according to the reaction below, what volume of oxygen gas (at STP) is produced? 

• 2KCLO3 ----> 2KCL + 3O2 
• 5.0 g x (1 mol/122.6 g) x (3/2) x (22.4L/1mol) = 1.4 L of O2 

Example Two: 

Find the amount of heat released when 5.0 mol of H2 are consumed according to the reaction:  

• N2 + 3H2 ---->  2NH3 + 46.2 kJ 
• 5.0 mol x (46.2 kJ/3) = 77 kJ

Find the amount of heat released when 250 g of Ammonia form according to the above reaction. 

• 250.0 mol x (1 mol/17.0g) x (46.2 kJ/2) = 3.4 x 10^2 kJ 

-Simon Sierra