What is a balanced chemical equation? How would you use the law of conservation of mass to explain why a chemical equation must be balanced?

1 Answer
Jun 12, 2016

In every chemical equation that has ever been performed, mass is CONSERVED. What does this mean?


Conservation of mass means that if I start with 10 g of reactant, from all sources, at MOST I can get 10 g of product. In practice, I am not even going to get that, because losses inevitably occur on handling. Since mass is a property of atoms and molecules, fundamental particles in other words, it follows that these masses are conserved during a chemical reaction.

Let's examine a simple(?) combustion reaction, that of pentane:

#underbrace(C_5H_12(l) + 8O_2(g) rarr 5CO_2(g) + 6H_2O(l))_"328 g of reactants yields 328 g of products"#

Is this balanced? How do you know? If it is balanced, then there is mass equivalence of reactants, #328*g# and products #??g#.

All of this are examples of stoichiometry. Stoichiometry insists that mass (and atoms and molecules) be balanced with respect to mass and charge.

#"Garbage in must equal garbage out"#.

Note that we practise stoichiometry all the time, For instance when we make a cash or electronic transaction; debits and credits are balanced. If they are not, someone will very soon notice.