A mole (mol) is a SI baseunit used to measure the amount of material in a chemical sample.
1 mole of H2O contains6.022 x 1023 H2O molecules (Avogadro’s number)
A coefficient in a balanced chemical equation indicates the number of moles of achemical compound involved in a chemical reaction. 2H2 + O2 2H2O
The coefficients give you themole ration of the compounds involved in the reaction. 2H2 + O2 2H2O The mole ratio of hydrogen to oxygen is 2:1 (for every oneoxygen put into the reaction, 2 moles of hydrogen are alsoneeded to put into the reaction)
The unit of moles provides a “bridge” to mathematically convertbetween several different aspects of chemical compounds.
Moles link an abstractchemical equation to a concrete unit ofmeasurement (grams, Liters, number of molecules)
For example:1 mole = 6.02 x 1023 molecules1 mole = molecular mass of a substance1 mole = 22.4 L of a substanceat STP (standard temperature and pressure)
For example:1 mol Cl = 6.02 x 1023 molecules Cl 1 mol H2O = 6.02 x 1023 molecules H 2O 1 mol Cl = 35.45g Cl 1 mol H2O = 18.01g H2O 1 mol Cl = 22.4L Cl @ STP 1 mol H2O = 22.4L H2O @ ATP
There are several types of calculations that can be used in Stoichiometry.
The object of this type ofproblem is to calculate the moles of one substancewhen given the number of moles of different substance.
Example: Magnesiumhydroxide reacts with carbonicacid. How many moles of water will be produced from 3.5 moles of magnesium hydroxide? You are given the moles of one substance and asked to find the moles of another substance.
Example: How many molesof ammonia can be producedfrom 8.00 moles of hydrogen reacting with nitrogen?
Example:K2Cr2O7 + 6KI + 7H2SO4 Cr2(SO4)3 + 4K2SO4 + 3I2 + 7H2O Calculate the number of moles of potassium dichromate that will react with 2.0 moles of potassium iodide. Calculate the number of moles of iodine that will be produced from 2.0 moles of potassium iodide.