Chemical+Equations

A chemical equation is a written way to express what happens during a chemical reaction. It tells you what is involved and gives you a way to measure the quantities associated with a reaction.

The general chemical equation is written like this: reactant + reactant product + product Not all reactions look exactly like this one. Some reactions only have one product and/or reactant. Others have many products and reactants. The reactants are written out in chemical formulas (for example, Carbon Dioxide becomes CO 2 ) There are also other parts of a chemical reaction. The coefficient goes in front of a chemical formula if there is more than one molecule of something. If there is one molecule, there is no need to include a coefficient of 1. It is understood to be there.
 * General formula:[[image:https://encrypted-tbn1.google.com/images?q=tbn:ANd9GcRRL0ET_v8iqEumTF1eTO3KncGXT-ljRHFeTcW2EFbwYfuetaMw width="208" height="152" align="right" caption="This is an example of a chemical equation with the different parts labeled. From http://www.mikeblaber.org "]]**

Some laws (for example, the Law of Conservation of Mass) put limits on how much can change over the course of a chemical reaction
 * Rules for chemical reactions:**
 * Things that must stay the same
 * Identity of atoms in the reactants must be the same as the identity of atoms in the products
 * The number of atoms in the reactants must be the same as the number of atoms in the products
 * The mass of all of the reactants must be the same as the mass of all of the products (keep in mind that this also includes gases that escape)
 * Things that can change
 * The number of molecules in the reactants vs. the number of molecules in the products (this is expressed by the coefficient)
 * Physical states of the reactants and/ or products (solid can become liquid, liquid can become gas and so on)

During a chemical reaction, even though elements may rearrange themselves there will always be the same number of atoms on the reactants side and the products side. For example, if there is one atom of oxygen on the reactants side of an equation, then there must be one atom of oxygen on the products side of the reaction. It doesn't matter if the oxygen is part of, say, an OH molecule on the reactants side and a CO molecule on the other side. All that matters is that there is one O on each side. To ensure that this rule is followed we have a process known as balancing equations.
 * Balancing chemical equations:**
 * 1) Determine how many atoms of each element are already accounted for in the chemical equation. To do this, make sure you count the subscripts as well as the coefficients (multiply the big number in front of the entire molecule by the small number following the element that you are interested in).
 * 2) Only use the coefficients when you balance equations (don't use the subscripts)
 * 3) Begin to balance the equation by changing the coefficients on both sides of the equation so that there are the same number of atoms of each element of both sides (Note: you can change the coefficients on either the products side, the reactants side, or both sides. It's all based of what leads to the best outcome).
 * 4) If an element is present in only one compound on both sides, balance it first.
 * 5) If there are molecules that have only one type of atoms in the entire compound, on one side (for example, if you see CO + 2Fe balance the Fe last).
 * 6) Balance polyatomic ions as a unit (don't worry too much about these if you're just learning).
 * 7) Always check your work. It is very easy to miss things in this process and checking your work early will save you lots of time and frustration.