Please enable JavaScript.
Coggle requires JavaScript to display documents.
rates of reaction + chemical bonding (Rates of reaction (effects of…
rates of reaction + chemical bonding
Rates of reaction
colission theory
in orders for a reaction to take place:
particles of the reactants
must collide with each other
collisions must provide
sufficient energy
for the reaction to ocure
(activation energy = minimum amount of energy required for a reaction)
particles need to collide at a
favourable angle
the frequency of successful collisions
determines the reaction rate
more succesful collisions per time
effects of
physical state/surface area
example;
cut up potatoes cook faster than whole potatoes
Why:
when there is a larger surface area there are
more exposed particles that are able to collide
and react. the number of collisions increases and therefore the number of successful collisions, hence the increasing rate of reaction
surface area:
(exposed) only particles on the outside of the reactant are able to collide and react with other particles of the other reactant
losts of small peice have a bigger surface area than one big pice ( if the combined volume is the same)
physical state
reactions in a solution generally proceed faster than reactions in a physical state - this is because the particles are free moving and this increase the collisions rate
effects of
concentration
Why:
higher concentration means
more particles in the same space
. This means the particles are
more likely to collide
, therefor successful collision rate increases and there higher rate of reaction
concentration
:
solutions of higher concentraiton
& gases at a higher pressure
= more (reactant) particles in the same volume
number of particles per unit volume
because there are more particles, they are closer together, and the
distance that must be travelled before they collide is decreased.
this means there are more frequent collisions
as the reaction continues the concentration of reactants decreases - therefore reaction rate decreases
effects of
temperature
example: things cooking faster at a high temperature
Why:
when temperature increases particles gain more energy because they have
more energy the particles move faster
and are more likely to collide with each other. Also the particles
have more energy no now they are more likely to have successful collisions
(reach sufficient activation energy). this increases the rate of reaction
temperature:
if temperature increases the average kinetic energy of the particles also increases, because they are moving faster.
-
a temperature rise of 10 degrees = 2x as many particles have the necessary activation energy (Ea) / the reaction rate doubles
the energy released from a reaction, suplies energy to reactants so the reaction continues (e.g. a fire continues to burn)
chemical bonding
formula
Balancing equations:
to balance equations,
you must
have equal numbers
of ions on both sides of the equation
subscript is only used to make formulas, not balance.
instead big numbers are put in front
How to write formula/rules
:
the positive ions attracts towards the negative ions, so the cation is written before the anion
the total charge must be zero (not neutral!)
an ionic compound contains very large numbers of ions, but the formula is written in the simplest ratio
the numbers of ions required is written as subscript (@ bottem)
brakets are written around polymatic ions
the charges of the ions are not written on the product of the compound
Examples:
Cu2+ Cl- = Cu Cl2
Zn2+ OH = Zn (OH)2
Fe3+ S2- = Fe2 S3
Al3+ No3- = Al (NO3)3
S = solid
L = liquid
g= gas
aq= aqueous /water solution
ratios of ions
so that the compound has a
charge of zero
A compound (substance that contains more than one element) is held together by chemical bonding
(only a few elements exist as separate atoms naturally)
it is a chemical bond that holds them together
ionic bonding vs. covalent bonding
ionic bonding
: ionic bonding forms ion /
found in ionic substances
exchanging elelcrons
between ions (give and take)
metals and non-metals do this
covalent bonding
: occurs between elements when molecules are formed/
found in molecular substances
shares electrons
between ions
only non-metals do
bonding:
when atoms approach, the nuclei repel each other (positive, charges, like charges repel) and the electrons also repel (negative opposition)
therefor; to form a chemical bond there must be opposite existing as the atoms come togeather (opp. charges atract)
all atoms what to gain full valence shell in order to become stable and unreactive when they bond. but to do this they must loose or gain electrons, with gives them a positive or negative charge.
ionic compounds:
ions of opposite charges attract each other
An
ionic compound is made up of ions with opposite charges,
exchanging electrons through an ionic bond
the ions are held togeather in a 3 dimentional arrangment/network
(the anions will be slightly begger than the cations becasue they have gained elelctrons)