Stoichiometry-problems
moles-stoichiometry-practice-problems Now you're ready to use what you know about conversion factors to solve some stoichiometric problems in chemistry. Almost all stoichiometric problems can be solved in just four simple steps:
1.Balance the equation.
2.Convert units of a given substance to moles.
3.Using the mole ratio, calculate the moles of substance yielded by the reaction.
4.Convert moles of wanted substance to desired units.
These "simple" steps probably look complicated at first glance, but relax, they will all become clear.
Let's begin our tour of stoichiometry by looking at the equation for how iron rusts:
Fe + O2→Fe2O3
Step 1. Balancing the Equation
The constituent parts of a chemical equation are never destroyed or lost: the yield of a reaction must exactly correspond to the original reagents. This fact holds not just for the type of elements in the yield, but also the number. Given our unbalanced equation:
Fe + O2→Fe2O3
This equation states that 1 iron (Fe) atom will react with two oxygen (O) atoms to yield 2 iron atoms and 3 oxygen atoms. (The subscript number, such as the two in O2 describe how many atoms of an element are in a molecule.) This unbalanced reaction can't possibly represent a real reaction because it describes a reaction in which one Fe atom magically becomes two Fe atoms.
Therefore, we must balance the equation by placing coefficients before the various molecules and atoms to ensure that the number of atoms on the left side of the arrow corresponds exactly to the number of elements on the right.
4Fe +3O2→2Fe2O3
Let's count up the atoms in this new, balanced version of the reaction. On the left of the arrow we have 4 atoms of iron and 6 atoms of oxygen (since 3×2 = 6 ). On the right we also have 4 iron (since 2×2 = 4 ) and 6 oxygen ( 2×3 = 6 ). The atoms on both sides of the equation match.
The process of balancing an
1.Balance the equation.
2.Convert units of a given substance to moles.
3.Using the mole ratio, calculate the moles of substance yielded by the reaction.
4.Convert moles of wanted substance to desired units.
These "simple" steps probably look complicated at first glance, but relax, they will all become clear.
Let's begin our tour of stoichiometry by looking at the equation for how iron rusts:
Fe + O2→Fe2O3
Step 1. Balancing the Equation
The constituent parts of a chemical equation are never destroyed or lost: the yield of a reaction must exactly correspond to the original reagents. This fact holds not just for the type of elements in the yield, but also the number. Given our unbalanced equation:
Fe + O2→Fe2O3
This equation states that 1 iron (Fe) atom will react with two oxygen (O) atoms to yield 2 iron atoms and 3 oxygen atoms. (The subscript number, such as the two in O2 describe how many atoms of an element are in a molecule.) This unbalanced reaction can't possibly represent a real reaction because it describes a reaction in which one Fe atom magically becomes two Fe atoms.
Therefore, we must balance the equation by placing coefficients before the various molecules and atoms to ensure that the number of atoms on the left side of the arrow corresponds exactly to the number of elements on the right.
4Fe +3O2→2Fe2O3
Let's count up the atoms in this new, balanced version of the reaction. On the left of the arrow we have 4 atoms of iron and 6 atoms of oxygen (since 3×2 = 6 ). On the right we also have 4 iron (since 2×2 = 4 ) and 6 oxygen ( 2×3 = 6 ). The atoms on both sides of the equation match.
The process of balancing an