Balancing+Equations

=Balancing Equations=

Look this is really JUST an accountancy exercise - try not to get too tied up with it. Again the secret is practise, practise, practise. One a night for a week for two weeks, followed by one every other night for a couple of weeks, and then a couple per week to keep your hand in.

If you want to suceed at A-level then put the ground work in NOW.

Here are some tips to get you started.

There are four easy steps that you need to follow to make this work. Here they are:


 * 1. Get yourself an unbalanced equation. ** I might give this to you, or I might make you figure it out for yourself. Either way, if you don't have an equation with all the chemical formulas and the arrow and all that other stuff, then you're out of luck.


 * 2. Draw boxes around all the chemical formulas. ** Never, ever, change anything inside the boxes. Ever. Really. If you do, you're **guaranteed** to get the answer wrong.


 * 3. Count the elements. ** How are you going to know if the equation is balanced if you don't actually make a list of how many of each atom you have? You won't. You have to make an inventory of how many atoms of each element you have, and then you have to keep it current throughout the whole problem. There are various ways to do this - find one that suits you and use it.

..
 * 4. Write numbers in front of each of the boxes until the inventory for each element is the same both before and after the reaction. ** Whenever you change a number, make sure to update the numbers of atoms - otherwise, you run the risk of balancing it incorrectly. When all the numbers in the inventory balance, then the equation can balance, and you can relax.

Here is an example...

Let's say I ask you the following thing on a test: "Balance the equation that takes place when sodium hydroxide reacts with sulphuric acid"

How do we solve this using the steps above?


 * 1. Get yourself an unbalanced equation. ** Here's where you use your knowledge of formulas to help you out. If you know what the formula of sodium hydroxide, sulphuric acid, AND you will need to recall the basic reactions of acids from KS3 - yes that long back!!! and therefore be able to confidently know that the prodcts are sodium sulphate and water and you can write their formula.

You'd be able to write the following unbalanced equation:




 * 2. Draw boxes around all the chemical formulas. ** This is the step that people frequently don't do because they feel that it's a stupid thing to do. Those people are the grade E candidates. Ignore them. You're drawing those boxes so that you'll be sure not to mess around with the formulas to balance the equation. While they all suffer in the pits of academic hell, you'll be laughing from joys of your awesome AS grade. Here's what the equation looks like:




 * 3. Count the elements**** . ** Your job is to figure out how many atoms of each element you have on the left and right sides of the equation. Now, if you look at the equation, you should be able to see that on the left side of the equation there is one sodium atom, five oxygen atoms (one from the sodium hydroxide, four from the sulphuric acid), three hydrogen atoms (one from the sodium hydroxide, two from the sulphuric acid), and one sulphur atom. On the right side of the equation, there are two atoms of sodium, one atom of sulphur, five atoms of oxygen (four from the sodium sulphate and one from the water), and two atoms of hydrogen. Thus, your element inventory should look like this:




 * 4. Write numbers in front of each of the boxes until the inventory for each element is the same both before and after the reaction. **

Now, what happens when we put a number in front of a formula? Basically, anything in that box is multiplied by that number, because we're saying that we have that many of that kind of molecule. So, looking at the numbers of atoms, what should we do?

Well, we can see that on the left side of the, there is one atom of sodium and on the right there are two. The solution: Stick a "**2**" in front of the sodium hydroxide on the left side of the equation so that the numbers of sodium atoms are the same on both sides of the equation. When we do this, the new atom count should look like this: (I'll let you figure out how this is done)



Now what? Well, looking at the new count, we can see that we now have two sodium atoms on both the left and the right sides, but the others still don't match up. What to do?

You can see from the count that on the right side of the equation, there are two hydrogen atoms and on the left there are four. Using your amazing powers of mathematics (and hopefully not needing to use a calculator), you can see that two multiplied by the number two becomes four. That's what you need to do. How?

Put a "**2**" in front of the water on the right side of the equation to make the hydrogens balance out. Now that this is done, you should make a new count that looks something like this:



Since both sides of the count match, the equation is now balanced! All other equations will balance in exactly the same way, though it might take a few more steps in some cases.

Practice questions - try this link.

or this link - where you can start with a beginner level and work your way up

and 20 questions to check your ability.