Stoichiometry Flashcards
Stoichiometry
The area of study that examines the quantities of substances consumed and produced in a chemical reaction.
Chemical Equations
Represent chemical reactions
+ sign in a chemical reaction means:
Reacts with
the —–> sign in a chemical reaction means:
Produces
Coefficients in a chemical equation
Indicate the relative number of molecules of each kind involved in the reaction
Reactants
the starting substance in a reaction
-on the left side of the arrow
Products
substances produced in the reaction
-on the right side of the arrow
Balanced equation
when there are equal numbers of atoms on each side of the chemical equation.
Symbols for state and what they mean:
(aq) aqueous
(g) gas
(l) liquid
(s) solid
Combination Reactions
when two or more substances react to form one product
Decomposition Reactions
When one substance undergoes a reaction to produce two or more other substances.
Combustion Reaction
rapid reactions that produce a flame and most have atmospheric O2(g) as a reactant reacting with a hydrocarbon and they produce CO2 (g), and often H2O.
quantitative Significance
the subscript and coefficients in the equation represent precise quantities.
Formula Weight
The sum of the atomic weights of the atoms in the chemical formula of the substance.
Molecular Weight
The mass of the collection of atoms represented by the chemical formula for molecule.
Formula Unit
is the mass of a collection of ionic substances.
–NaCl for example
Percentage Composition
the percentage by mass contributed by each element in the substance
Percentage Composition of an element formula
(((Number of atoms of element)x(Atomic Weight of element))÷(Formula Weight of Substance))x 100
Mole (mol)
the counting unit for numbers of atoms, ions, or molecules in a laboratory-size samples
Avogadros’s Number
6.022 x 10^23
Molar Mass
the mass in grams of one mole of a substance (g/mol)
Procedure to find the empirical formula
Mass % of element -(assume 100g sample) Grams of each element -use molar mass Moles of each element -calculate mole ratio Empirical Formula
How to find the Molecular formula from the Empirical Formula
Whole-number multiple = Molecular Weight ÷ Empirical Formula Weight
Limiting Reactant
the reactant that is completely consumed in a reaction
Excess reactant
the other reactants that are not the limiting reactant
Theoretical yeild
the quantity of product calculated to form when all of a limiting reactant is consumed
Percent Yield
relates actual and theoretical yeilds
Percent yield formula
Percent yield =
(actual yield ÷ Theoretical yield) x 100
