a) REACTION RATES by j3CZ5d

VIEWS: 17 PAGES: 13

									UNIT 1
                                                                                                          Can
a) REACTION RATES                                    Learning Outcomes                                          Notes
                                                                                                           Do
(i) Following the course of a reaction
Reactions can be followed by measuring  State that the rate of reaction may be expressed in
changes in concentration, mass and          terms of the changes in concentration of reactants or
volume of reactants and products.           products in unit time.
The average rate of a reaction, or stage  Calculate the average rate for a given time interval
in a reaction, can be calculated from       from initial and final concentrations and the time
initial and final quantities and the time   interval.
interval.
The rate of a reaction, or stage in a      State that the average rate for the initial stages of
reaction, is proportional to the            a reaction is related to 1/t (t = time).
reciprocal of the time taken.
(ii) Factors affecting rate
The rates of reactions are affected by     State that for many reactions the rate is
changes in concentration, particle size     proportional to the concentration(s) of reactants.
and temperature.                           State that a small rise in temperature can result in a
                                                large increase in rate.
The collision theory can be used to            Explain reactions of molecules in terms of
explain the effects of concentration and        rearrangement of bonds when the molecules collide
surface area on reaction rates.                Explain the effect of changing concentrations in
                                                terms of the number or reacting molecules.
                                               Explain the effect of particle size on reaction rate in
                                                terms of surface area(s) of reactant(s).
Temperature is a measure of the                State that temperature is a measure of the average
average kinetic energy of the particles         kinetic energy of the molecules of a substance.
of a substance.


                                                                       1
a) REACTION RATES                                 Learning Outcomes                              Can   Notes
                                                                                                 Do
(ii) Factors affecting rate (contd.)       
The activation energy is the minimum        State that the activation energy is the
kinetic energy required by colliding         minimum kinetic energy required by colliding
particles before reaction will occur.        molecules before reaction will occur.
Energy distribution diagrams can be         Draw and explain energy distribution diagrams to
used to explain the effect of changing       show the effect of changing temperature on the
temperature on the kinetic energy of         kinetic energy of molecules.
particles.
The effect of temperature on reaction       Explain the effect of temperature on rate in
rate can be explained in terms of an         terms of an increase in the number of molecules
increase in the number of particles with     with energy greater than the activation energy.
energy greater than the activation
energy.
With some chemical reactions, light can be used to increase the number of particles with
energy greater than the activation energy.

(iii) The idea of excess
The reactant that is in excess can be       Carry out calculations which involve
calculated.                                  identification of reactants that are in excess.
(iv) Catalysts
Catalysts can be classified as either       State differences between heterogeneous and
heterogeneous or homogeneous.                homogeneous catalysis.
Catalysts are used in many industrial       Give examples of key catalysts, including enzymes
processes.                                   used in industry.
Heterogeneous catalysts work by the         Explain how surface catalysts work in terms of
adsorption of reactant molecules.            adsorption of molecules.


                                                                    2
a) REACTION RATES                                 Learning Outcomes                             Can   Notes
                                                                                                Do
(iv) Catalysts (contd)
The surface activity of a catalyst can be  Explain what is meant by catalyst poisoning in
reduced by poisoning.                        terms of preferential absorption.
Impurities in the reactants result in the
industrial catalysts having to be
regenerated or renewed.
Catalytic convertors are fitted to cars
to catalyse the conversion of poisonous
carbon monoxide and oxides of nitrogen
to carbon dioxide and nitrogen.
Cars with catalytic converters only use     Give a common example of catalyst poisoning.
‘lead-free’ petrol to prevent poisoning of
the catalyst.
Enzymes catalyse the chemical reactions which take place in the living cells of plants and
animals.
Enzymes are used in many industrial         Give examples of key catalysts including enzymes
processes.                                   used in industry.

(b) Enthalpy                                      Learning Outcomes                             Can   Notes
                                                                                                Do
(i)   Potential Energy Diagrams
Exothermic changes cause heat to be          State that endothermic changes cause
released to the surroundings;                 absorption of heat from the surroundings.
endothermic changes cause absorption
of heat from the surroundings.


                                                                   3
 (b) Enthalpy (contd.)                          Learning Outcomes                              Can   Notes
                                                                                               Do
A potential energy diagram can be used     Explain exothermic and endothermic reactions
to show the energy pathway for a            with the aid of potential energy diagrams.
reaction.
The enthalpy change is the energy          State that enthalpy change is the energy
difference between products and             difference between products and reactants.
reactants.
The enthalpy change can be calculated      Calculate enthalpy change from a potential
from a potential energy diagram.            energy diagram.
The enthalpy change has a negative         State that the enthalpy change has a negative
value for exothermic reactions and a        value for exothermic reactions and a positive
positive value for endothermic              value for endothermic reactions
reactions.
The activated complex is an unstable       State that the activated complex is an unstable
arrangement of atoms formed at the          arrangement of atoms formed at the maximum of
maximum of the potential energy             the potential energy barrier, during a reaction
barrier, during a reaction.
The activation energy is the energy        State that the activation energy is the energy
required by colliding molecules to form     required by colliding molecules to form an
an activated complex.                       activated complex.
The activation energy can be calculated    Work out activation energy from potential energy
from potential energy diagrams.             diagrams.
The effect of a catalyst can be            Explain catalytic effect in terms of alternative
explained in terms of alternative           reaction pathways with lower activation energy.
reaction pathways with lower activation
energy.



                                                                4
(b) Enthalpy                                       Learning Outcomes                               Can   Notes
                                                                                                   Do
A potential energy diagram can be used       Draw a potential energy diagram to show the
to show the effect of a catalyst on           effect of a catalyst on activation energy.
activation energy.
(ii) Enthalpy changes
The enthalpy of combustion of a              State that the enthalpy of combustion of a
substance is the enthalpy change when         substance is the enthalpy change when one mole
one mole of the substance burns               of the substance burns completely in oxygen.
completely in oxygen.
The enthalpy of solution of a substance      State that the enthalpy of solution of a
is the enthalpy change when one mole of       substance is the enthalpy change when one mole
the substance dissolves in water.             of the substance dissolves in water.
The enthalpy of neutralisation of an acid    State that the enthalpy of neutralisation of an
is the enthalpy change when the acid is       acid is the enthalpy change when the acid is
neutralised to form one mole of water.        neutralised to form one mole of water.
The enthalpy changes can be calculated         Calculate loss or gain of heat energy using
using cmΔT.                                     cmΔT.
c) Patterns in the Periodic Table                                                                  Can
                                                   Learning Outcomes                                     Notes
                                                                                                   Do
The modern Periodic Table is based on the work of Mendeleev who arranged the known
elements in order of increasing atomic masses in conjunction with similar chemical properties,
leaving gaps for yet to be discovered elements.
There are variations in the densities,         Explain data on metallic character, density,
melting points, and boiling points of the       melting point, and boiling point for elements 1-
elements across and down a group.               20 in terms of the type of bonding and
                                                structure


                                                                    5
c) Patterns in the Periodic Table                                                                      Can
                                                   Learning Outcomes                                         Notes
                                                                                                       Do
The atomic size decreases across a             State that the covalent radius of an element is
period and increases down a group.              half the distance between the nuclei to two of its
                                                bonded atoms.
                                               Explain the decrease in covalent radius across a
                                                period in terms of increasing nuclear charge.
                                               Explain the increase in covalent radius down a
                                                group in terms of number of occupied energy
                                                levels.
The first ionisation energy is the enegry      State that the first ionisation enthalpy of an
required to remove one mole of                  element is the energy required to remove one
electrons form one mole of gaseous              electron from each atom in a mole of atoms in the
atoms.                                          gaseous state.
The second and subsequent ionisation        
energies refer to the energies required
to remove further moles of electrons.
The trends in the first ionisation energy      Explain variations in the first ionisations enthalpy
across periods and down groups can be           of the elements across periods and down groups
explained in terms of the atomic size,          in terms of the distance of the outermost
nuclear charge and the screening effect         electrons from the nucleus, the size of the
due to inner shell                              nuclear charge, screening effect and stability of
Electrons.                                      full outer energy levels.
Atoms of different elements have               State that atoms of different elements have
different attractions for bonding               different attractions for bonding electons.
electrons..


                                                                     6
c) Patterns in the Periodic Table                  Learning Outcomes                             Can   Notes
 (contd)                                                                                         Do
Electronegativity is a measure of the attraction an atom involved in a bond has for the
electrons of the bond.
Electronegativity values increase across a      Relate attraction of bonding electrons to the
period and decrease down a group.                position of an element in the Periodic Table.
d) Bonding, structure and
properties
(i) Types of bonding

Metallic bonding is the electrostatic           Explain metallic bonding in terms of the
force of attraction between positively           eledcrostatic attraction of a lattice of
charged ions and delocalised outer               positively charged ions and loosely-held
electrons.                                       electrons.
Atoms in a covalent bond are held            
together by electrostatic forces of
attraction between positively charged
nuclei and negatively charged shared
electrons.
The polarity of a covalent bond depends         State that a difference in attraction for
on the difference in electronegativity           electrons between bonded atoms results in a
between the bonded atoms.                        polar bond.
Ionic bonding is the electrostatic force        State that an ionic lattice is a structure of
of attraction between positively and             oppositely charged ions electrostatically
negatively charged ions.                         attracted to each other.

                                                                   7
d) Bonding, structure and                           Learning Outcomes                             Can   Notes
properties (contd)                                                                                Do
The type of bonding in a compound is             State that elements widely separated in the
related to the positions of its                   Periodic Table are likely to form ionic
constituent elements in the Periodic              compounds
Table.
(ii) Intermolecular forces of attraction      
Van der Waals’ forces are forces of              State that van der Waals’ forces are
attraction which can operate between all          attractions between atoms or molecules and
atoms and molecules.                              are much weaker than all other types of
                                                  bonding.
Van der Waals’ forces are much weaker            State that van der Waals’ attractions, in the
than all other types of bonding.                  absence of other types of intermolecular
                                                  attraction, are important
Van der Waals’ forces are a result of electrostatic attraction between temporary dipoles and
induced dipoles caused by movement of electrons in atoms and molecules.
The strength of van der Waals’ forces is related to the size of the atoms or molecules.

A molecule is described as polar if it has a permanent dipole.

Permanent dipole - permanent dipole interactions are additional electrostatic forces of
attraction between polar molecules.
The spatial arrangement of polar covalent        State that a polar molecule contains polar
bonds can result in a molecule being polar.       bonds which are not symmetrically opposed


                                                                    8
d) Bonding , structure and                        Learning Outcomes                              Can   Notes
properties (contd)                                                                               Do
Bonds consisting of a hydrogen atom            Explain hydrogen bonding in terms of
bonded to an atom of a strongly                 intermolecular attractions which are found in
electronegative element such as fluorine,       compounds containing hydrogen bonded to an
oxygen or nitrogen are highly polar.            atom with a strong attraction for bonding
                                                electrons
Hydrogen bonds are electrostatic forces
of attraction between molecules which
contain these highly polar bonds.
A hydrogen bond is stronger than other forms of permanent dipole- dipole
interaction but weaker than a covalent bond.
(iii) Structure
A metallic structure consists of a giant       Explain metallic bonding in terms of the
lattice of positively charged ions and          electrostatic attraction of a lattice of
delocalised outer electrons.                    positively charged ions and loosely-held outer
                                                electrons
A covalent molecular structure consists        State that a covalent molecule is a discrete
of discrete molecules held together by          entity whereas a covalent network is a large
weak intermolecular forces.                     lattice structure.
A covalent network structure consists of       State that van der Waals’ attractions and
a giant lattice of covalently bonded atoms.     attractions between polar molecules, including
                                                hydrogen bonding, are intermolecular forces.
An ionic structure consists of a giant         State that an ionic lattice is a structure of
lattice of oppositely charged ions.             oppositely charged ions electrostaticallyt
                                                attracted to each other.


                                                                  9
d) Bonding, structure and                             Learning Outcomes                                Can   Notes
properties (contd)                                                                                     Do
A monatomic structure consists of                State that noble gases are monatomic.
discrete atoms held together by van der          State that van der Waals’ forces are
Waals’ forces.                                    attractions between atoms or molecules and
                                                  are much weaker than all other types of
                                                  bonding.
                                                State that van der Waals’ attractions , in the
                                                 absence of other types of intermolecular
                                                 attraction, are important.
The first 20 elements in the Periodic         State the category of bonding and structure
Table can be categorised according to        for elements 1- 20 in the Periodic Table
bonding and structure:
 metallic (Li, Be, Na, Mg, Al, K, Ca)
 covalent molecular (H2, N2, O2, F2, Cl2,
   P4, S8 and C (fullerenes))
 covalent network (B, C (diamond,
   graphite), Si)
 monatomic (noble gases)
Compounds each adopt one of three             State that a covalent molecule is a discrete entity
structures in the solid state:                 whereas a covalent network is a large lattice
   covalent molecular                         structure.
   covalent network, including silicon         State that an ionic lattice is a structure of
       dioxide and silicon carbide               oppositely-charged ions electrostatically attracted
   ionic                                        to each other.
                                                Describe the structures of covalent network
                                                 compounds, including silicon dioxide and silicon
                                                 carbide.


                                                                      10
d) Bonding, structure and properties                                                                Can
                                                  Learning Outcomes                                       Notes
(contd)                                                                                             Do
(iv) Properties
The melting points, boiling points and      Explain data on metallic character, density, melting
hardness/softness of elements and            point and boiling point for elements 1-20, in terms
compounds are related to their bonding       of the type of bonding and structure.
and structures.                             Relate hardness and uses of ;silicon carbide to its
                                             structure
                                            Explain pattern in the M.P. B.P.state of oxide at
                                             room temperature and electrical conduction of melt
                                             of oxides of elements of the second and third
                                             periods, in terms of their structure and tupe of
                                             bonding.
The melting and boiling points of polar     Explain the difference in boiling point between
substances are higher than the melting       polar and non-polar substances with similar
and boiling points of non-polar              molecular mass.
substances with similar molecular sizes.
Ionic compounds and polar molecular         Explain that some molecules with polar bonds,
compounds tend to be soluble in polar        (e.g. hydrogen halides) ionise in aqueous
solvents such as water and insoluble in      solution.
non-polar solvents.
Non-polar molecular substances tend to      State that, in general, polar and ionic
be soluble in non-polar solvents and         substances are soluble in polar solvents, and
insoluble in polar solvents.                 insoluble in polar solvents.
The anomalous boiling points of ammonia,    Explain the anomalous boiling point of water in
water and hydrogen fluoride are a result     relation to the other Group 6 hydrides by
of hydrogen bonding.                         reference to hydrogen bonding.


                                                                  11
d) Bonding, structure and properties                                                               Can
                                                       Learning Outcomes                                 Notes
(contd)                                                                                            Do
Boiling points, melting points, viscosity and    Explain the anomalous boiling point of HF and
miscibility in water are properties of            NH3 in relation to the trend within their
substances which are affected by hydrogen         respective groups, in tens of hydrogen
bonding.                                          bonding.
Hydrogen bonding between molecules in ice        Describe the arrangement of water molecules
results in an expanded structure which            in ice and relate this to the density being
causes the density of ice to be less than         lower than that of water.
that of water at low temperatures.
The uses of diamond, graphite and silicon        Explain the properties of diamond and
carbide are related to their structures and       graphite in terms of the structure of each.
properties.                                      Relate hardness and uses of silicon carbide to
                                                  its structure.
 Fullerenes are the subject of current research and applications are being sought

                                                       Learning Outcomes                           Can   Notes
The Mole
                                                                                                   Do
(i) The Avogadro Constant
One mole of any substance contains               State that the mole is that amount of a given
6.02x1023 formula units.                          substance which contains as many elementary
                                                  entities as there are carbon atoms in 12g of
                                                  carbon-12. (The elementary entities must be
                                                  specified and may be atoms, molecules, ions
                                                  electors or other particles.)
                                                 State that the number of specified
                                                  elementary entities in one mole of any
                                                  substance is the same ( 6.02x1023)

                                                                    12
                                                   Learning Outcomes                              Can   Notes
The Mole
                                                                                                  Do


                                            

Equimolar amounts of substances contain
equal numbers of formula units.
(ii) Molar volume
The molar volume (in units of mol l-1) is    State that the molar volume (in units of volume
the same for all gases at the same            per mole)is the same for all gases at the same
temperature and pressure.                     temperature and pressure.
The volume of a gas can be calculated        Calculate a molar volume from given data and
from the number of moles and vice versa.      apply this to link number of moles to volume.
(iii) Reacting volumes                      

The volumes of reactant and product          Carry out calculation involving balance equations
gases can be calculated from the number       and volumes of gaseous reactants or products,
of moles of each reactant and product         recognising liquid or solid products and assuming
                                              them to have negligible volume.




                                                                    13

								
To top