Post on 04-Jan-2016
description
Stoichiometry
Involves the mass relationships between reactants and products in a
chemical reaction.
Problem Type 1
• Given and unknown quantities are amounts in moles.
• This is a mol mol calculation.• To solve these problems you need the mole ratio = a conversion factor that relates the amounts in moles of any two substances in a chem Rxn.
Example
• Ammonia, NH3, is widely used as a fertilizer and as an ingredient in many household cleaners. How many moles of ammonia are produced when 6 mol of hydrogen gas react with an excess of nitrogen gas?
H2 + N2 NH3
Problem Type 2
• Given is in moles and unknown is expressed in grams (mass).
• This is a mol mol mass conversion calculation.
Example
• When magnesium burns in air, it combines with oxygen to form magnesium oxide according to the following equation
2Mg + O2 2MgO
What mass is grams of MgO is produced from 2 moles of Mg?
Problem Type 3
• Given is a mass in grams and unknown is in moles.
• This is a mass mol mol calculation.
Example
• Oxygen was discovered when heated mercury (II) oxide decomposed to form its constituent elements. How many moles of HgO are needed to produce 125 g of oxygen, O2?
Problem Type 4
• Given and unknown amounts are in grams (mass).
• This is a mass mol mol mass calculation.
Example
• When copper metal is added to silver nitrate in solution, silver metal and copper (II) nitrate are produced. What mass of silver is produced from 100g of Cu?