Week 3 - The Mole and Balancing Chemical Equations

Chemical engineers and chemists use the term "mole" for quantity measurements in their work. For example, one mole of water (H2O) weighs 18.0 grams or the sum of the gram formula weight of two hydrogens and one oxygen (2 x 1.00797 + 1 x 15.9994, rounded off to 18.0 grams). There are 6.02 x  1023 carbon atoms in one mole of water. See the Periodic Table for the gram formula weights for each element. Then one mole of sodium chloride (NaCl) or salt has a weight of 58.5 grams ( 22.9898 grams for sodium + 35.453 grams of chloride, rounded off to 58.5 grams).

                                                        
Regarding chemical reactions and the equations that illustrate the process, an equation has to be balanced on both sides. For example, when carbon dioxide (CO2)  is combined with sodium hydroxide (NaOH) (reactants), it yields  Na2CO3 and H2O (products).

                               CO2(gas) +2NaOH (solid) yields Na2CO3(solid) +H2O  (liquid)

To have the same number of elements on each side of the equation, a "2" must be inserted in front of the NaOH (2NaOH). This results in one carbon, four oxygens, two sodiums, and one hydrogen on each side. So one mole of  CO2 combined with 2 moles of NaOH yield one mole of  Na2CO3 and one mole of H2O. The ratio is as follows: 1 : 2 : 1 : 1.

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