Q44E - Chemistry (OpenStax)

Question

Although the gas used in the oxyacetylene torch Figure (5.7) is essentially pure acetylene, the heat produced by the combustion of one mole ofacetylene in such a torch is likely, not equal to the enthalpy of combustion of acetylene listed in the table 5.2. Considering the conditions for which the tabulated data are reported. Suggest an explanation.

Step-by-Step Solution

Answer

The heat produced by the combustion of one mole of acetylene in such a torch is likely not equal to the enthalpy of combustion of acetylene. 

This is because, in a torch, the combustion of acetylene does not occur at the standard condition for temperature, pressure, gases, etc.

Step 1: Temperature

The temperature in the torch is much higher than 25^oC.

Step 2: Gases

The gases are supplied from compressed gas cylinders.

Step 3: Pressure

The pressure of oxygen gas is greater than the standard pressure.

Step 4: Nature of the reaction

The reaction in which heat is expelled from the reaction is called an exothermic reaction.

 

The burning of acetylene and oxygen is exothermic.