Stoichiometry Flashcards
What must we use because we use large amounts of molecules and atoms in the real world?
Average masses in calculations
What is average atomic mass also known as?
atomic weight
How is the average atomic mass calculated?
Calculated from the isotopes of an element weighted by their relative abundances.
What is the percentage of an element that is 1 isotope called?
natural abundance
When is mass spectrometry used?
It is used when the masses of atoms and the percent abundances of isotopes of elements are measured.
What is mass spectrometry?
separates particles according to their mass
What is a mole (mol)?
a counting unit
What does moles help with?
Help provide a bridge from the real world scale to the molecular scale.
What is Avogadro’s number?
6.022 x 10^23
What does a mole allow us to relate?
mass to atoms of a substance
What is molar mass?
It is the mass of 1 mol of a substance (g/mol)
Where do we find the molar mass of an element?
on the periodic table
What is an empirical formula?
the lowest whole-number ratio of atoms of each element in a compound
What is percent composition?
the percentage by mass contributed by each element in the substance
Are the formulas obtained from percent compositions always the empirical formula?
YES ALWAYS
What is a molecular formula?
Gives the exact number of atoms of each element in a compound
What are chemical equations?
concise representations of chemical reactions
What do letters in parentheses represent?
states of matter
Where are the reactants and products located in a chemical equation?
reactants: left side
products: right side
What do the subscripts tell you in a chemical euqation?
the number of atoms of each element in a molecule
What do the coefficients tell you in a chemicals equation?
tell the number of molecules (used to balance equation)
Which of the following quantities must always be the same on both sides of a chemical equation?
- same number of atoms of each kind
- the sum of the masses of all substances involved
What is stoichiometry?
the quantitative study of the amounts of reactants and products in chemical reactions
