Module 3 Flashcards
what is periodicity
the repeating pattern seen across different periods
advantages and disadvantages of numbering the groups 1-7
+ve group number matches number of electrons in highest energy shell
-ve doesn’t include d-block
advantages of numbering groups 1-18
+ve numbers each column in the s, p and d blocks sequentially
what is the s block
groups 1 and 2
s-subshells being filled
what is the p block
groups 13-18
p-subshells being filled
group 18 are inert as their subshells are filled
what is the d block
transition metals
define first ionisation energy
energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms
factors affecting ionisation energy
atomic radius
nuclear charge
shielding
how does ionisation energy increase across the periodic table
from bottom left to top right
from bottom to top, from left to right
what evidence do ionisation energies provide
shell structure that supports the Bohr model of the atom
and that subshells fill in a particular order
why does hydrogen have a high 1st ionisation energy
as the electron is closest to the nucleus and has no shielding
what is second ionisation energy
energy needed to remove 1 electron from each ion In 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
what happens to melting and boiling points across periods 2, 3 and 17
increases from Li to C
increases from Na to Si
increases from F2 to At2
what happens to melting and boiling points as you go down the periodic table
decrease
what happens to the atomic radius across a periodic table
decreases
what happens to the atomic radius as you go down the periodic table
increases
why does reactivity decrease down group 17
because its harder for it to attract an extra electron into its outer shell and be reduced to form a 1- ion, due to increased shielding and a larger atomic radius, which decrease the effective nuclear charge
what colour to the halide ions turn when silver nitrate is added
cl- white precipitate
br- cream precipitate
I- pale yellow precipitate
what happens to the halide ions when dilute and conc. ammonia are added
cl- dissolves in dilute
br- dissolves in conc.
I- insoluble
define disproportionation
oxidation and reduction of the same element in a redox reaction
chlorine and water equation
Cl2 + H2O –> HClO + HCl
can purify drinking water
chlorine and alkali equation
Cl2 + 2NaOH –> NaClO + NaCl + H2O
define enthalpy
amount of energy that a substance contains
what is an exothermic reaction
gives heat to surroundings
displayed as a -ve enthalpy
what is an endothermic reaction
energy being taken in from surroundings
displayed as a +ve enthalpy
what is the equation for energy transferred
q=mcΔT
define activation energy
the minimum energy required for a reaction to take place
how to calculate enthalpy of reaction
∑(bond enthalpies of reactants) - ∑(bond enthalpies of products)
define enthalpy of neutralisation
enthalpy change when an acid and alkali react together to form 1 mole of water
what is Hess’ law
if a reaction can take place by more than one route, the total enthalpy change is the same for each route
describe the collision theory
particles constantly moving
reactant particles must collide
the particles must have a minimum amount of energy- activation energy- and the correct orientation for the collision to be effective
factors that affect rate of reaction
concentration (pressure if reactants are gas)
temperature
catalyst
surface area
how does concentration affect rate of reaction
more particles in a given volume, increasing frequency of successful collisions
how can rate of reaction be measured
volume of gas produced
mass of reactants
colour change
what is a homogenous catalyst
is the same physical state as the reactants
what is a heterogeneous catalyst
different physical state to the reactants
benefits of catalysts in terms of sustainability
lower temperatures required, so less energy demanded and less combustion of fossil fuels
this reduces CO2 emissions and sustainability is improved
factors of the Boltzmann distribution curve
total area under the graph represents the total number of molecules
shaded area represents the number of molecules with enough energy to react if they collide
what happens to the Boltzmann curve when temperature increases
curve gets broader and shaded area increases as more molecules have the activation energy or higher
what is dynamic equilibrium
reversible reaction where rate of the forward reaction is equal to the rate of the backward reaction
what is Le Chatelier’s principle
equilibrium shifts in position to favour the forward or backward reaction- opposes change
what factors affect the position of equilibrium
change in concentration
change in pressure
change in temperature
what way does equilibrium shift when pressure is increased
to the side with fewer gas molecules
what way does equilibrium shift if temperature is increased
in the endothermic direction
how to calculate equilibrium constant- Kc
concentration of products/ concentration of reactants
aA + bB — cC + dD
Kc= [C]c[D]d/[A]a[B]b
[A]= conc of A inn moldm-3 a= number of moles of A
what does it mean if the value of K>1
the reaction is product-favoured
what does it mean if the value of K<1
the reaction is reactant-favoured
uses of cobalt chloride
humidity indicator in weather instruments
cobalt chloride paper tests for the presence of water
what do catalysts do
provide an alternative route with a lower activation energy
name for group 2 elements
alkaline earth metals
name for group 17 elements
halogens
standard conditions
298k
100KPa
what is the atomic radius
the distance from the outer shell of electrons to the nucleus of the atom
what is shielding
number of shells of electrons between the nucleus and outer shell of electrons
what is nuclear charge
the attraction from the protons in the nucleus with the electrons
what is the standard enthalpy change of a reaction
the enthalpy change when the amounts shown in the chemical equation react under standard conditions with the reactants and products in their standard states
what is the standard enthalpy change of combustion
the enthalpy change when 1 mole of the substance completely burns in an excess of oxygen under standard conditions with the reactants and their products in their standard states
what is the standard enthalpy change of formation of a compound
the enthalpy change when 1 mole of the compound forms from its elements under standard conditions with the elements in their standard states
what is bond dissociation enthalpy
the enthalpy change on breaking 1 mole of a particular covalent bond in a gaseous molecule
as you go down group 2 what happens to solubility
it increases
which sulphate in group 2 is the most insoluble
BaSO4
how to test for sulphates
add acid and BaCl
what detects halogen ions
AgNO3
what colour do the halogens go when hexane is added
Cl2- pale green
Br2- orange
I2- purple
