ABSTRACT
In chemical reactions, including combustion, mass is conserved. That is to say, mass is neither created nor destroyed during the combustion reaction: 100 kg of fuel
+
1000 kilograms of air will generate 100
+
1000 (
=
1100) kg of products. Notwithstanding, the species will change. For example, one can write a reaction for methane (CH
) combustion with oxygen as follows:
CH
+
2O
Æ
CO
+
2H
O (4.1)
The subscripted numbers refer to the number of elements in a given molecule. Oxygen molecules are diatomic (comprising two oxygen atoms). The antecedent numbers refer to the number of molecular entities. A molecular entity with no antecedent number is presumed to refer to a single molecule. Hence, Equation 4.1 shows that one molecule of methane (CH
) reacts with two molecules of oxygen (2O
) to produce one molecule of carbon dioxide (CO
) and two molecules of water (2H
O). Equation 4.1 is a
balanced
equation, meaning that the left and right sides of the equation comprise identical amounts of each element, C, H, and O. However, the molecular species have changed. On the left side, CH
and O
are present; on the right side, CO
and H
O.
