Unit 4 Flashcards
what is the purpose of avogadros number
When doing mathematical calculations with billions and billions of atoms and molecules, it can be difficult to keep track of such large numbers. To make chemical calculations easier, chemists created a new unit.
what is the symbol fro avogadros number
NA
what is avogadros #
6.022 x 10^23
who came up with avogadros #
Amedeo Avogadroin 1811
who calculated avogadro’s #
The German scientist Johann Josef Loschmidt first calculated the value of Avogadro’s number in 1865.
why did chemist devolp the mole
Chemists developed their own unit for grouping large quantities of small particles such as atoms, molecules, and ions—the mole.
what is a mole
The mole, whose abbreviation is “mol”, is the base unit for measuring and standard method in chemistry for communicating how much of a substance is present.
define mole
A mole is defined as the amount of a substance that contains the same number of entities (atoms, molecules, formula units) as exactly the number of atoms in 12 grams of carbon-12.
give an example of how big a mole is
1 mole of watermelon seeds would be about the size of the moon.
How to convert moles to number of particles:
of moles (n) x Avogadro’s # = number of particles
How to convert number of particles to moles:
of particles (N) / Avogadro’s # (NA) = # of moles (n)
what is mass
The mass of an atom mainly comes from its protons and neutrons
what is the molecular mass
The molecular mass, or molecular weight, of a substance is the mass in atomic mass units of all the atoms in a given molecule.
what is the molar mass
The mass of one mole of a substance is referred to as its molar mass and is expressed in grams per mole. The symbol for molar mass is M.
how to convert moles to mass
of moles (n) x molar mass (M) = mass (m)
how to convert mass to moles
mass (m) / molar mass (M) = # of moles (n)
how to convert the number of particles to mass
Step 1: # of particles / NA = moles
Step 2: # of moles (from above) x molar mass (M) = mass (g)
how to convert mass to number of particles
Step 1: mass (m) / molar mass (M) = moles (n)
Step 2: Moles (from above) x NA = # of particles
solutions define
Solutions are homogeneous mixtures of two or more pure substances made by dissolving one substance, called the solute, into another substance, called the solvent.
what is the most common solvent
liquid water
what is concentration
The concentration of a solution provides information about the strength of the solution
what is concentrations symbol
C
what is concentrations unit of measurment
PPM PPB % of mass % of volume g/L
how to calculate concentration
c = x (original amount) / v (volume)
define molarity
concentration
what is molarity
the concentration of moles/litre
how to calculate molar concentration
c = moles / litre
what is the equation for dilution
Vi x Ci = Vf x Cf
what is stoichiometry
the study of the amount of reactants and products involved in chemical reactions
how is stoichiometry used in chemistry
In stoichiometry, mole ratios from balanced chemical equations are used to calculate or predict the quantities of reactants used or products produced.
what is the mole ratio
(known moles) / (unknown) = (coefficient of known) / (coefficient of unknown)
what is percentage yeild
the ratio of the actual yield to the theoretical yield expressed as a percentage
what is theoretical yield
the amount of product produced in a chemical reaction calculated from the balanced chemical equation
what is the actual yield
the amount of product that actually forms when the reaction is carried out in the laboratory
what is the percentage yield formula
actual yield / theoretical yield x 100%
what is a limiting reactant/reagent
the reactant that runs out first therefore stopping the reaction
