Skeleton Equation

Skeleton Equation vs. Balanced Equation

Before we get into what a skeleton equation is, let's review chemical reactions. In chemical reactions, the bonds between atoms in the reactant side are broken, and new bonds are formed, creating new substances.

$$ \text{Reactant + Reactant } \longrightarrow \text{ Products} $$

When a chemical reaction happens, any of the following might occur:

• Changes in temperature.
• Changes in color.
• Formation of gases, bubbles, or odor.
• Formation of a solid (precipitate).
• Energy release.

Chemists use Chemical Equations to represent these changes happening in a chemical reaction.

For example, the chemical equation between the reactants Carbon monoxide gas (CO) and oxygen gas (O₂) to yield Carbon dioxide (CO₂) is shown below:

$$ \text{2 CO + O}_{2} \longrightarrow 2 \text{ CO}_{2} $$

Chemical Equations follow the law of conservation of mass. According to this law, the mass of the products is always the same as the mass of the reactants. Therefore, chemicals equations must be balanced to make sure the law of conservation of mass in being followed.

Let's look at an example!

Skeleton Equation Definition

Now that we know what balanced equations are, let's look at the definition of a skeleton equation.

As an example, let's look at the chemical reaction between iron (Fe) and chlorine gas (Cl₂) to yield iron (III) chloride (FeCl₃). The skeletal equation for this reaction would be:

$$ \text{Fe }(s)\text{ + Cl}_{2}\text{ } (g) \longrightarrow \text{FeCl}_{3}\text{ }(s) $$

Now, if we were to balance this equation, we would get:

$$ \text{2 Fe }(s)\text{ + 3 Cl}_{2}\text{ } (g) \longrightarrow \text{2 FeCl}_{3}\text{ }(s) $$

How to Write a Skeleton Equation

To write a skeleton equation, all you need to do is know the reactants you are dealing with and the product it forms!

For example, if you were told that there was a chemical reaction happening between aluminum and oxygen in which aluminum oxide was formed, you can use this word equation to write the reaction's skeleton equation.

Skeleton equation: \(\text{Al} (s) \text{ + O}_{2}(g) \longrightarrow \text{Al}_{2}\text{O}_{3}(s)\)

Balanced equation: \( \text{4 Al} (s) \text{ + 3 O}_{2}(g) \longrightarrow \text{2 Al}_{2}\text{O}_{3}(s) \)

Let's solve a problem!

Skeleton Equation of Methanol

Now that we've discussed skeleton equations and how to write them, let's look at some skeleton equations involving methanol (CH₃OH).

Methanol is a liquid at STP, and it is miscible in water. It is considered a volatile liquid alcohol, and it widely used as antifreeze and fuel. The Lewis structure of methanol is shown below:

Let's first look at the chemical reaction between methanol and water. In this reaction, carbon dioxide and hydrogen gas are produced! The skeleton equation for this reaction is as follows:

\text{CH}_{3}\text{OH + H}_{2}\text{O} \rightleftharpoons \text{CO}_{2}\text{ + H}_{2}

When methanol is allowed to react with oxygen, it forms formaldehyde (HCHO) and hydrogen peroxide (H₂O₂) as products. Formaldehyde is a colorless gas produced by the oxidation of methanol. It is considered poisonous.

The skeleton equation in this case is

\( \text{CH}_{3}\text{OH + O}_{2} \longrightarrow \text{HCHO}\text{ + H}_{2}\text{O}_{2} \).

Now, what happens when methanol (CH3OH) reacts with a metal like sodium? The reaction between methanol and sodium (Na) yields sodium methoxide and hydrogen!

Skeleton equation:

\( \text{CH}_{3}\text{OH + Na}\longrightarrow \text{NaOCH}_{3}\text{ +}\text{ H}_{2}\)

Balanced equation:

\( \text{2 CH}_{3}\text{OH + 2 Na}\longrightarrow \text{2 NaOCH}_{3}\text{ +}\text{ 3 H}_{2}\)

Skeleton Equation Examples

To finish off, let's look at some examples involving the skeleton equation of some important chemical reactions.

For example, in biology, some bacteria (such as H. pylori) are able to degrade urea (H₂NCONH₂) into ammonia (NH₃) and carbon dioxide (CO₂)

Skeleton equation:

\( \text{H}_{2}\text{NCONH}_{2} + \text{H}_{2}\text{O} \longrightarrow \text{NH}_{3} +\text{ CO}_{2}\)

Balanced equation:

\( \text{H}_{2}\text{NCONH}_{2} + \text{H}_{2}\text{O} \longrightarrow \text{2 NH}_{3} +\text{ CO}_{2}\)

Another interesting chemical reaction is the formation of ozone (O₃), which occurs when a monatomic oxygen molecule (O) combines with a diatomic oxygen molecule (O₂). Ozone is a gas that is commonly produced by the action of UV radiation on oxygen in the stratosphere, causing its photodissociation. The earth's ozone layers acts a screen, blocking most UV radiation coming form the sun.

Skeleton equation:

\(\text{O + O}_{2}\longrightarrow \text{O}_{3}\)

Balanced equation:

\( \text{O + 2 O}_{2}\longrightarrow \text{2 O}_{3}\)

I hope you've now got a better idea of what a skeleton equation is!