Periodic Table And Energy Flashcards
How are elements arranged in a periodic table
They’re arranged in the order of increasing atomic numbers
What is meant by periodicity
Repeating trends in chemical and physical properties
Define first ionisation energy
The energy required to remove one electron from each atom in one mole of the gaseous element to form one mole of gaseous 1+ ions
What are the factors that effect ionisation energy
Atomic radius
Nuclear charge
Electron shielding of screening
Why does first ionisation energy decrease between group 2 to 3
In group 3 outermost electrons are in p orbital whereas in group 2 they’re in s orbital so electrons are easier to remove
Does first ionisation increase or decrease between the end of one period and the start of the next
Decrease because
Increase in atomic radius
Increase in electron shielding
Does first ionisation Increase or decrease down a group
Decrease because
Shielding increases
Atomic radius increases
What’s the most reactive metal of group 2
Barium
3 physical properties of group 2 metals
High melting and boiling points
Low density metals
Form colorless compounds
Does reactivity increase or decrease down group 2
Increases- electrons are lost more easily because larger atomic radius and more shielding
What are the products when group 2 elements react with water
Hydroxide and hydrogen gas
What is oxidised and what is reduced in a reaction between group 2 metal and water
Metal- oxidised
Hydrogen from each water - reduced
What is formed when group 2 oxides react with water
Metal hydroxide
List 2 properties of halogens
Low melting and boiling points
Exist as diatomic molecules
Trend in boiling point down group 7
Increases because size of atom increases
More electrons(more London forces)
Trend in reactivity down group 7
Decreases because
Atomic radius increases
Electron shielding increases
Ability to gain electron decreases
Define disproportionation
The oxidation and reduction of the same element in a redox reaction
Why is chlorine added to drinking water
Kills bacteria in the water and makes it safer to drink
How can you test for carbonate Ions
Add strong acid to the sample
Collect the gas produced
Pass through lime water
Positive test- carbonate ions
Fizzing
Lime water turns cloudy
Test for sulfate ions
Dilute hydrochloric acid and barium chlorine to the sample
Test for sulfate ions
Dilute hydrochloric acid and barium chlorine to the sample
Positive test- sulfate ions
White precipitate
Test for halide ions
Dissolve sample in water
Add aqueous silver nitrate
Record colour change
If difficult to distinguish colour add aqueous ammonia
Note solubility
Positive result- halide ions
Cl-: white precipitate
Br-: cream precipitate
I-: yellow precipitate
Order or qualitative tests
Carbonate,sulfate,halide
Test for ammonium ions
Sodium hydroxide and warm
Test gas with red litmus paper
Positive ammonium test
Red litmus paper turns blue
Ammonia smells
What does a system mean in a chemical reaction
The atoms and bonds involved in the chemical reaction
Explain the law of conservation
The amount of energy I am isolated system remains the same. Energy cannot be destroyed or created if can only be transferred
What energy change is breaking bonds associated with
Energy is taken in to break bonds- endothermic
What energy change is making bonds associated with
Energy is released to make bonds- exothermic
What is an endothermic reaction
A reaction with an overall positive enthalpy change
What is an exothermic reaction
A reaction with an overall negative enthalpy change
What does activation energy mean
The minimum energy required for a reaction to take place
What are standard conditions
100kPa
298K
What does in standard state mean
The state an element/ compound exists at in standard conditions
Define enthalpy change of formation
The energy change that takes place when 1 mole of a compound is formed from its constituent elements in their standard state under standard conditions
Define enthalpy change of combustion
The energy change that takes place when 1 mole of a substance is completely combusted
Define enthalpy change of neutralisation
The energy change that takes place when 1 mole of water is formed from a neutralisation reaction
What does enthalpy change of reaction mean
The energy change associated with a given reaction
How can you calculate enthalpy change from experimental data
Q=mc🔺️T where m is mass of substance being heated c is the specific heat capacity of that substance and 🔺️T is the change in temperature
What are the advantages of using a bomb calorimeter
Minimises heart loss
Pure oxygen used ensures complete combustion
Why might experimental methods for enthalpy determination not be accurate
Heat is lost to surroundings
Not in standard conditions
Reaction may not go to completion
What does average bond enthalpy mean
The mean energy required to break 1 mole of bonds in gaseous molecules
How to calculate enthalpy change of reaction using average bonds enthalpies
🔺️H=sum of(bond enthalpies of reaction)- sum of (bond enthalpies of products)
What is the equation used to calculate rate
Rate=change in concentration/ time
Unit for rate of reaction
Mol dm^-3 s ^-1
What must particles do in order to react
Collide with sufficient energy and correct orientation
Do most collisions result in a reaction
No
Factors that effect rate of reaction
Temperature
Pressure
Concentration
Surface area
Catalyst
Affect of temperature on rate
Higher proportion of particles have energy greater than the activation energy so more successful collisions
Increasing pressure/ concentration on rate
More particles in a given volume
How to calculate rates from a concentration time graph
Draw a tangent
Work out gradient
Change in y/ change in x
What is catalyst
A substance which increases the rate is reaction but is not used up in the reaction
How do catalysts work
They provide an alternate reaction pathway so more particles have sufficient energy so increases the reaction rate
Homogenous catalyst
A catalyst in the save phase as reactants
heterogeneous catalyst
Catalyst in a different phase to reactants
Catalytic convertors
Present in vehicles to reduce toxic emissions and prevent photochemical smog
Define activation energy
Minimum energy needed for a reaction to occur
Features of Boltzmann distribution
Area under curve=total number of molecules
Curve starts at the origin
Curve does not touch energy axis
Only molecules with energy more than the activation energy can react
Dynamic equilibrium
Rate of forward reaction equals rate of reverse reaction and concentration of reactants and products remain constant in a closed system
What factors effect the position of equilibrium
Concentration of reactants/ products
Pressure
Temperature
Le Chatelier’s principle
If a system at equilibrium is disturbed the equilibrium moves in the direction that tends to reduce the disturbance
What effect does a catalyst have on the position of equilibrium
No effect
What condition effects the value of Kc
Temperature
What type of system is Kc relevant for
Homogenous systems in equilibrium
What does Kc mean for the position of equilibrium
Greater than one = over to the right
Less than one= to the left
Effect of temperature on equilibrium
Increase temp= shifts to endothermic reaction
