# Chemistry balancing skeleton equations

#### rachelm

The balanced equation is H2 + CI2 —> 2HCI
There are two hydrogen (H) atoms on the reactants side and two chlorine (CI) atoms on the reactants side. One hydrogen (H) atom and one chlorine (CI) atom is produced. To balance them, we put a coefficient of 2 in front of the product hydrogen chloride (HCI).

Does this do a good job of showing my work for balancing the skeleton equation?

#### studiot

No, because you have missed something out that was in the original equation.

#### rachelm

No, because you have missed something out that was in the original equation.
You mean in the explanation??

#### rachelm

It produces two hydrogen atoms and two chlorine atoms??

#### studiot

$$\displaystyle {H_2}(g) + C{l_2}(g) \to 2HCl(g)$$

What happened to the (g) ?

topsquark

#### rachelm

$$\displaystyle {H_2}(g) + C{l_2}(g) \to 2HCl(g)$$

What happened to the (g) ?
That’s how it is balanced in my book..

#### studiot

Can you not see the difference between what you have written and what is written in your book ?

Do you know what (g) means and why that information might be important?

rachelm

#### rachelm

yes (g) indicates gaseous state but this is how it looks in my book.

#### studiot

OK
Getting the number of atoms of each type correct on both sides of the equation is one part of balancing

It is called the mass balance

So yes you have a total of 2 atoms of hydrogen combined in one hydrogen molecule on the left hand side
and a total of 2 atoms of hydrogen combined in 2 hydrogen chloride molecules on the right hand side.

etc.

The (g) tell us that there are 2 molecules (one each of hydrogen and chlorine) of gas on the left hand side
and 2 molecules of gas (both of hydrogen chloride) on the right hand side.
So there is no change to the amount of gas and no change of volume or phase (state).
Now every chemical reaction has an energy balance ( that is not stated in your book) and the fact that there is no change to the number of gaseous molecules means that there is no volume change and therefore there is no mechanical energy (work) involved in this reaction
So all the energy either absorbed or evolved is in the form of heat.
A full statement of the reaction would add +energy to teh right hand side thince this reaction evolves heat (is exothermic)

The first two types of balance are introduced in elementary Chemistry in the England

Finally there is another form of balance, called charge balance.

This is because sometimes either some products or some reactants or both are ionic or charged.

In this case both the reactants and products are electrically neutral so the charge balance is zero = zero.

Charge Balance is introduced in High School Chemistry in England

rachelm

#### rachelm

So how should I show my work for this type of problem?