What is not true about most combustion reactions? a) elemental carbon is a product b) energy is released c) a carbon-based fuel is a reactant d) molecular oxygen is a reactant

It would be A bc carbon is NOT usually a product. You can find out more about the by searching combustion reactions, then u should be able to answer the questions on your own.

The correct answer is Option a.

Explanation:

Combustion reaction is defined as the reaction in which a hydrocarbon reacts with oxygen gas to produce carbon dioxide gas and water molecule. It is considered as an exothermic reaction as energy is released during these reactions.

A hydrocarbon is a substance which contains a covalent bond between a hydrogen and carbon atoms. So, it is considered as a carbon-fuel compound.

The general equation for this reaction follows:

From the above equation, it is visible that elemental carbon is not produced.

Hence, the correct answer is Option a.

c is the answer because when something is left after something evaporates that shows the chemical change.