How do you balance a chemical equation and why would you want to?

Question

I've not studied chemistry before and get confused when I see diagrams with arrows and elements. Are you able to give me a simple example to work through, explaining the need to balance in the first place. Maybe dissolving salt into water? Something like that would be great. I know water is H2O, salt is CaCl2+ (I think?) or perhaps you have a better example to use?

Answer 1

The reason you balance chemical equations is to keep your chemistry teacher happy!

Seriously, things do not always react in a 1 to 1 ratio! It is necessary to have a balanced equation in order to know the ratio in which the various starting materials react, in the creation of the product(s). This ratio needs to be in terms of numbers of atoms/molecules (moles) to enable calculation of such things as: quantities of reactants necessary to create the product, also, when calculating things such as which material is the limiting reagent, how much product can be made from a stated amount of staring materials, how much material would be left over after the reaction is done etc, etc.

For example combustion of propene CH3CH=CH2.

C3H6 + O2 ---> CO2 + H2O (un-balanced)

You can see you need 3 O2's for the burning the carbon part of the propene, and you need 1 1/2 O2's for burning the hydrogen part of the propene:

C3H6 + 4 1/2 O2 ---> 3 CO2 + 3 H2O

But it is necessary to have whole numbers for the balanced equation, so in some cases, such as this one, we need to double everything:

2 C3H6 + 9 O2 ---> 6 CO2 + 6 H2O

Once it is balanced, we can use the moles of reactants and the reaction ratios to carry out all kinds if calculations concerning the reaction.

If someone were to ask how many moles of water would be formed from burning 1 mole of propene you could now easily see that you would get 3 moles of water:

1 mole propene x (6moles water/2moles propene) = 3 moles

water

Having this ability now allows the calculation of grams of products, reactants, volumes of gases evolved, or final pressure (if contained), concentrations of final solutions etc etc.

Answer 2

The answer to HOW you balance an equation is to make sure you have the same number of elements on each side of the equation. For example, NaCl + AgNO3 ==> AgCl + NaNO3 (sodium chloride + silver nitrate ==> silver clhloride + sodium nitrate). Note that both sides of the equation have the same number of Na Cl Ag and NO3. This was a simple example, but sometimes it gets more complicated.

WHY do we NEED to balance these equations? So that we can calculate how much to add, and how much we expect to get at the end. Now, it you aren't a chemist, then you could probably care less.

Answer 3

Well for all I know, balancing is essential. The balancing is normally required by the scientists to make the products of a reaction. Scientists can use the accurate values from the equation to make a pure and proper product without wasting any elements or compounds.

Example
H2SO4 + Zn ---> ZnSO4 + H2
Equation balanced

2Mg + 1O2 -- > 2MgO

Happy new year!!!!!!!!!