Chemical Reactions-Translate word equations


How do we balance the equation?
Balancing chemical equations isn't difficult, once you know the way to do it.

Start by finding out how many atoms of each type are on each side of the equation. Some teachers recommend making a little table listing the numbers of each atom for the left hand side and for the right hand side.

Next, look for an element which is in only one chemical on the left and in only one on the right of the equation.

To balance that element, multiply the chemical species on the side which doesn't have enough atoms of that type by the number required to bring it up to the same as the other side. The number is called the coefficient.

BUT

If you have to multiply by, say, 2 1/2, do so, THEN multiply EVERYTHING on each side of the equation by two to get rid of the half.

Now look for the next element or species that is not balanced and do the same thing.

Repeat until you are forced to balance the hydrogen and oxygens.

If there is a complex ion, sometimes called a polyatomic ion, on each side of the equation that has remained intact, then that can often be balanced first, as it is acts as a single species. The ions NO3- and CO32- are examples of a complex ion.

A VERY useful rule is to leave balancing oxygen and hydrogen to the last steps as these elements are often in more than one chemical on each side , and it is not always easy to know where to start. Some people also say you should leave any atom or species with a valancy of one one until the end, and also generally leave anything present as an element to the end.

Example 1
Unbalanced equation:- H2SO4 + Fe ---> Fe2(SO4)3 + H2
Balance the SO4 first (as it is a complex ion and it is in one chemcial species on each side)
3H2SO4 + Fe ---> Fe2(SO4)3 + H2
Now balance the Fe (which is also in one chemical on each side)
3H2SO4 + 2Fe ---> Fe2(SO4)3 + H2
Finally, balance the hydrogen (although it is in one chemical species on each side, it is usually a good idea to leave it until last)
Balanced Equation:- 3H2SO4 + 2Fe ---> Fe2(SO4)3 + 3H2

Example 2
Unbalanced Equation:- Al + O2 ---> Al2O3
We can start with either the Al or the O, but we will start with Al, as we normally leave O to the end. Even though it wouldn't matter where we started in this case.
Put a two in front of the Al on the left
2Al + O2 ---> Al2O3
Put a 1 1/2 in front of the O2 on the left
2Al + 1 1/2O2 ---> Al2O3
We don't like halves, so multiply everything on BOTH sides by two
4Al + 3O2 ---> 2Al2O3