Balancing Chemical Equations

A Chemical Reaction

Check out this reaction: Cesium and Water

Check out this reaction: Cesium and Water

Cs + H2O CsOH + H2 Here is one way to read the reaction:

Cs + H2O CsOH + H2 Cesium combines with water to give you cesium hydroxide and hydrogen gas Or…………

Cs + H2O CsOH + H2 One mole of cesium combines with 1 mole of water to give one mole of cesium hydroxide and one mole of hydrogen gas. This is better but not perfect.

Cs + H2O CsOH + H2 What is wrong with this reaction as it is written?

Cs + H2O CsOH + H2 Answer these 4 simple questions: How many grams are there in one mole of cesium? One mole of water? One mole of cesium hydroxide? One mole of hydrogen gas?

Cs + H2O CsOH + H2 One mole of cesium = 132.9 grams One mole of water = 18.0 grams One mole of cesium hydroxide = 149.9 grams One mole of hydrogen gas = 2.0 grams

Cs + H2O CsOH + H2 Add the reactants together: 132.9 + 18.0 = 150.9 grams 149.9 + 2 = 151.9 grams

Cs + H2O CsOH + H2 What the hell??!!??!!?? You have just created 1.0 grams of matter. That’s impossible!

“Matter cannot be created nor destroyed in a chemical reaction “Matter cannot be created nor destroyed in a chemical reaction!” said this guy

_Cs + _H2O _CsOH + _H2 This equation is not “balanced” You balance equations by changing the coefficients or number of moles of each reactant and product, if necessary. Coefficients are the numbers before each reactant and product. If a number is not there, it is a ‘1’.

_Cs + _H2O _CsOH + _H2 Any easy way to check if an equation is balanced is to create an atom inventory. This is done by counting all the atoms of each type of reactant and product.

_Cs + _H2O _CsOH + _H2 1 Cs 1 Cs 2 H 3 H 1 O 1 O We can see that the equation is not balanced.

_Cs + _H2O _CsOH + _H2 1 Cs 1 Cs 2 H 3 H 1 O 1 O We must change the coefficients so that this inventory is the same for the reactants and products. You can put any number 2 or higher in any of those 4 spaces to “balance” the equation.

_Cs + 2H2O _CsOH + _H2 1 Cs 1 Cs 4 H 3 H 2 O 1 O When you change a coefficient, make sure you change your inventory.

_Cs + 2H2O 2CsOH + _H2 1 Cs 2 Cs 4 H 4 H 2 O 2 O When you change a coefficient, make sure you change your inventory.

2Cs + 2H2O 2CsOH + _H2 2 Cs 2 Cs 4 H 4 H 2 O 2 O This equation is now balanced. The number of atoms of reactants equal the number of atoms of products.

2Cs + 2H2O 2CsOH + _H2 The masses of reactants and products will also equal one another

2Cs + 2H2O 2CsOH + _H2 2 moles of Cs = 265.8 grams 2 moles of water = 36.0 grams 301.8 grams of reactants

2Cs + 2H2O 2CsOH + _H2 2 moles of CsOH = 299.8 grams 1 moles of H2 = 2.0 grams 301.8 grams of products

2Cs + 2H2O 2CsOH + _H2 Mass of reactants = Mass of products Perfect. The way you say this reaction is………………

2Cs + 2H2O 2CsOH + _H2 2 moles of cesium combines (or reacts) with 2 moles of water to form 2 moles of cesium hydroxide and 1 mole of hydrogen gas.

Try to balance these equations: H2 + Cl2 HCl NaI + Br2 NaBr + I2 Al + Fe2O3 Al2O3 + Fe

Now this one: C4H10 + O2 CO2 + H2O