Ask Me Help Desk - Combustion?

Hi!

I just made an experiment today. We had some liquids (Acid, bases, alcohols) and some solids (metals, salts) and we had to mix them, in order to find some gas-forming reactions. After finding them, we had the write the balanced equations and analyze the reaction.

We could also burn the solids (or the liquids) with a bunsen burner.

I decided to burn ammonia (NH3), Potassium Chlorate (KClO3) and sucrose (C12H22O11). My big question is : Is oxygen a reactant in the reaction, or only a product? Because, if it is, then is it possible to have the same element on both sides of a chemical equation?

Example (not balanced but you get the idea):

KClO3(solid) + O2 (gas) = O2 (gas) + KCl (solid)?
or
KClO3 (solid) + heat = O2 (gas) + KCl (solid)?

Same thing for sucrose and NH3.

Thank you!

If you are burning anything then oxygen is a reactant in the equation.

Hope this helped!! Roll Tide!

1. If you have oxygen on both sides of an equation, you can cancel them out. For example, if you have 3 moles of oxygen on the left but only 2 on the right, that is equivalent to having only one mole on the left and none on the right.

2. KClO3 is an oxidizer. O2 is an oxidizer. KClO3 won't normally react with O2 (It is possible to form perchlorate, KClO4, but it takes a very strong oxidizer and oxygen isn't strong enough).

$KClO_3 (+ heat) \rightarrow KCl + \frac 32 O_2$ This is a simple decomposition reaction.

You can assume this as an intermediate in order to figure out what happens when sucrose burns in KClO3. If you don't have enough KClO3 around, but there is air, then you'll have the decomposition of KClO3 and the reaction with oxygen.

$C_{12}H_{22}O_{11} + 12 O_2 \rightarrow 12 CO_2 + 11 H_2O$

BAMAstudent is NOT correct that oxygen is always a reactant in burning. You can burn in a vacuum if you supply an oxidizer (like potassium chlorate, for example). Explosives provide their own (usually solid, occasionally liquid) oxidizers. They burn and they do not rely on air. Similarly, you can burn hydrocarbons and other materials in chlorine (and other halogens) to form chlorinated hydrocarbons. This is commonly done on an industrial scale.