Compounds and Stoichiometry Flashcards by Sayan Basu

Compounds

pure substances made of two or more elements

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Molecule

combination of two or more atoms (same or different) held together by covalent bonds

smallest unit of compounds

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Ionic compounds do not form true molecules because…

of the way ions orient themselves in the solid state

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Formula Weight (amu)

weight of a ionic compound as it has no molecules

sum of atomic weights of the constituent IONS in compound

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Molecular Weight (amu)

sum of all atomic weights of the ATOMS in a molecule

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Mole

quantity of substance (atoms) equal to the number of particles found in for example 12 grams of Carbon or 16 grams of oxygen

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Avogadros Number

number of particles, 6.022*10^23

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one mole of a compound has a mass in grams equal to the ______ of a compound in amu

molecular/formula weight

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Molar Mass (g/mol)

mass of one mole of compound ; not same as molecular weight

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g = n * MM

Mass = moles * Molar Mass

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Equivalents Examples

HCL - 1 mole of H
H2SO4 - 2 moles of H
H3PO4 - 3 moles of H

Na - 1 mole of electrons
Mg - 2 moles of electrons

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Gram Equivalent Weight

amount of a compound (in grams) that produces one equivalent of particle of interest

Gram Equivalent = Molar Mass of compound / moles of particle within ccompound

ex: GEW = 62/2 = 31g for H2CO3

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Determining Number of Equivalents in a Compound

Equivalents = Mass of Compound/ Gram Equivalent Weight

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Normality (N)

measure of concentration

N = equivalents / L

ex: 1 N solution of acid = 1 mole per liter of Hydrogen

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Normality and Molarity Relationship

Molarity = Normality / number of particles produced/consumed by solute

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Structural Formula

show bonds between constituent atoms of compound

all atoms present but not necessarily how they are oriented and the bonds present

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Law of Constant Composition

any pure sample of given compound will contain same elements in an identical mass ratio

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Empirical Formula

simplest, whole number ratio of elements in the compound

ex: CH for benzene

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Molecular Formula

gives the exact number of atoms of each element in the compound and is a multiple of the empirical formula

ex: C6H6 for benzene

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Ionic compounds only have Empirical/Molecular Formulas

Empirical as the total number of atoms cannot be determined

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Percent composition

percent o a specific compound that is made up of a given element

% = (Mass of element in formula / molar mass of ocompound) * 100

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Determining Empirical/Molecular Formulas from Percentages

1) Find molecular weight

moles C = (% in decimal)(MM of compound) / (MM of C)
moles of H = ….

2) round to nearest whole number to find mole ratio
3) find empirical b dividing by highest common divisor
ex: C6H9 -> C2H3

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Combination Reactions

two or more reactants forming one product

Decomposition Reactions

single reactant breaks down into two or more products with intervention of energy/catalyst/enzyme

Combustion Reaction

involves a fuel (hydrocarbon) and oxidant (oxygen) often produce CO2 and water

Single Displacement Reaction (Oxidation Reduction Reactions)

when an atom/ion in a compound is replaced by an atom or ion of another element ; known as oxidation reduction reactions ex: Cu(s) + AgNO3(aq) -> Ag(s) + CuNO3 (aq)

Double Displacement Reaction (Methathesis Reaction)

elements from two different compounds swap places with each other to form 2 new compounds Occurs when one of the products is removed from the solution as a precipitate/gas or when two of the original species combine to form a weak electrolyte that remains undissociated in solution ex: CaCl2 (aq) + 2 AgNO3 (aq) -> Ca(NO3)2 aq + 2 AgCl (s)

Neutralization Reactions

type of double displacement where an acid reacts with base to produce a salt and water HCl + NaOH -> NaCl (s) + H2O (l)

Balancing Chemical Equations

C4H10 + O2 ->CO2 + H2O 1) Balance one of the elements on side with less of the element C4H10 + O2 -> 4CO2 + H2O 2) Balance the second element on side with less of the element C4H10 + O2 -> 4CO2 + 5H2O 3) Balance the third element on side with less of the element C4H10 + 13/2 O2 ->4 CO2 + 5 H2O 4) Produce a whole number ratio 2 C4H10 + 13 O2 -> 8 CO2 + 10 H2O

Limiting Reagent

reactant that limits the amount of product formed as it is the first one used up

Excess Reagents

reactant(s) that are left after all limiting reagent is used

Theoretical Yield vs Actual Yield

maximum amount of product generated from balanced equation what you actually get

Percent Yield

(actual yield/ theoretical yield) *100%

Cations and anions are usually...

metals and nonmetals respectively

Nomenclature Ions: More than one positive ion

charge is indicated with roman numerals in parenthesis Cu+ is Copper(I) Cu2+ is Copper (II)

Nomenclature Ions: More than one positive ion with suffix

-ous for lesser charge, -ic for greater charge Ferrous Cuprous Ferric Cupric

Nomenclature Ions: Monatomic Anions

named by droping eneding of the name of element and adding -ide Hydride, Fluoride, Oxide, Sulfide, Nitride, Phosphide

Nomenclature Ions: Oxyanions Suffix

polyatomic anions with oxygen (usually 2 forms); one with less oxygen is -ite and one with more oxygen is -ate Nitrite (NO2)- Sulfite (SO3) 2- Nitrate (NO3)- Sulfate (SO4)2-

Nomenclature Ions: Oxyanion Prefix

used in extended series hypo- and per- for the lowest and highest respectively Hypochlorite ClO- Chlorite ClO2- Chlorate ClO3- Perchlorate ClO4

Nomenclature Ions: Polyatomic Anions with Hydrogen

gain hydogen to lower charge, gain prefix of hydrogen or dihydrogen HCO3- hydrogen carbonate

NH4+

Ammonium

C2H3O2-

Acetate

CN-

cyanide

MnO4-

permanganate

SCN-

Thiocyanate

CrO42-

chromate

Cr2O72-

dichromate

BO3 3-

borate

Oxidation States

different charged states of ionic species

Group 1 and Group 17

+1 charges and -1 charges respectively

Anionic species that contain oxygen with metallic species/halogens, those have ___ oxidation states

positive

Color of a solution can be indicative of the ______ of a given element in the solution

oxidation state

Solid ionic compounds tend to be ____ conductors of electricity because the charged particles are rigidly set in place by ______

poor ; lattice arrangement

Lattice arrangement in aqueous solutions is disrupted by

ion-dipole interactions between ionic compounds and the water molecules

Electrolytes

solutes that enable solutions to carry currents a strong electrolyte is if it completely dissociates into ions

Solvate

tendency of an ionic solute to dissolve into its constituent ions

Compounds with highly polar covalent bonds....

dissociate into ions when dissolved