Question

The gas sometimes used in laboratory burners is methane and the combustion produces carbon dioxide gas and water vapour.

A) use delta Gf data to calculate the Delta G rxn for the balanced reaction.

B) what would the value of Delta grxn be if the pressure of O2 were decreased to 0.3 atm from 1.00atm, at room temperature if all other gases remained at standard conditions.

C) explain why it is necessary to add a flame or spark to ignite methane in the lab?

Answer 1

A) CH4 + 2O2 → CO2 + 2H2O ...... balenced reaction

Delta G rxn = delta G _product - delta G _reactant

CO2 = -394.39 KJ/mol

H2O = -228.4 KJ/mol

O2 = 0

CH4 =  -74.85 KJ/mol

Delta G rxn =  (-394.39 KJ/mol) + 2(-228.4 KJ/mol) - ( -74.85 KJ/mol) = -776.34 KJ/mol

B) not change because standard gibbs free energy of O2 is 0

C) The gas then flows up through the base through a small hole at the bottom of the barrel and is directed upward. There are open slots in the side of the tube bottom to admit air into the stream via the venturi effect, and the gas burns at the top of the tube once ignited by a flame or spark. The most common methods of lighting the burner are using a matchor a spark lighter.