reactions and stoichiometry Flashcards
avogadro’s number
there are 6.02E23 molecules in a mole
molar mass units
g/mol
molecular formula
ex: SF6
- gives the number of atoms of each element in a compund
empirical formula
reduced form of molecular formula
ex: glucose empiracle formula is C(h2O)
percent composition by mass
mass of element/ mass of compound
problem situation: find the empirical formula for a compound that is 54% carbon, 9% H and 36% oxygen
assume 100 grams
54g/ 12 = 4.5 m carbon
9 mol hydrogen
36/16 o = 2.25 o
C2H4O
** to get number of each atom, divide each by the smallest amount of moles
chemical reaction
one or more chemical species are converted into one or more chemically different species
- bond breaking and reforming
- atoms themselves do not change
phase changes
physical process, not chemical and is reversible
reaction types on the mcat
synthesis
decomposition
single displacement
double displacement
neutralization
combustion
oxidation reduction
redox
synthesis reaction (combustion)
two or more reactants combine to form 1 product
A + B –> AB
decomposition rections
reverse of synthesis reactions
breakdown of a reactant into two smaller products
AB –> A+B
ENDOTHERMIC
breaking of bonds is typically (endo/exothermic)?
endothermic
-requires energy
displacement reaction
one element or gropu replaces another within a compound
- if only 1 group changes : single
- 2 groups exchange : double
single displacement formula
A + BC –> B + AC
2K + ZNCl3–> 2KCl + Zn
what species typically replaces in a double displacement
halogens and metals
methathesis
double replacement reaction when an insoluble product is formed
neutralization reaction
an acid and base react with eachother to form water and a salt
HCl + NaOH –> H2O + NaCl
combustion reaction
compound burns in the presence of elemental oxygen, non oxygen is burned and turned into fuel
- highly exothermic reacitons
c3h8 +o2 –> co2 + h2o
real life examples of combustion reactions
organic compounds of hydrogen and carbon are burned and produce carbon diozide and water
products of combustion reaction
h2o and co2
- very exothermic
oxidation reduction reactions
transfer of e- from one species to another
- both reactants experience a change in oxidation state
oxidation number
the charge that atom would have if the compound were composed of ions
limiting reagent
the lesser reactant that determines how much of the product can be formed
- determines amount of product
- reacts completely
non-limiting reagent
in excess, does not determine amount of product formed
how is the limiting reactant identified
using stoichiometry, calculate the amount of product made from each starting reactant and which ever one is less (in moles), is the limiting reactant
- must measure same product
- remember to balance equations
percent yield equation
actual mass/ theoretical mass x 100
alkali metals always have an oxidation number of what?
1+
alkali earth metals always have an oxidation number of what
2+
flourine oxidation number
1-
when does hydrogen not have an oxidation state of 1+
naH and liah4
oxygen usual oxidation numnber
2-
