General revision Flashcards
What is the definition of molar volume of gas?
The space occupied by one mole of gas at standard conditions (room temperature and standard pressure)
What is the effect on temperature on molar mass?
- as temperature decreases, molar mass increases
- at a lower temperature, there would be more moles in the same volume (greater density)
What is dry gas?
Gas without water vapour
What do you change in a reaction to make a product have a higher oxidation state?
The temperature (increase it)
Why does having a longer chain length increase the boiling point?
There is larger surface area and therefore contact, meaning there are stronger London forces, which require more energy to break
Why is there difference in bond lengths between two covalent substances?
- the longer bond length will have a larger atomic radius, and so a greater level of shielding
- this reduces the attraction for the bonding electrons causing a longer bond length
What is the ideal gas equation?
pV = nRT
What is the unit of p in the ideal gas equation?
Pascals
What is the units of volume in the ideal gas equation?
M^3
What is the ideal gas constant?
8.31
What bonding + lone pairs are in a linear bond shape?
- 2 bond pairs
- 0 lone pairs
What is the bond angle in a linear bond shape?
180
What are the electron pairs like in a bent bond angle?
- 2 bonding pairs
- 2 lone pairs
What is the bond angle in a bent bond shape?
104.5
What is the bond angle in a triangular planar shape?
120
What are the electron pairs like in a triangular planar?
- 3 bonding pairs
- 0 electron pairs
What is the bond angle in a trigonal pyramidal?
107
What are the electron pairs like in a trigonal pyramidal?
- 3 bonding pairs
- 1 lone pair
What is the bond angle in a tetrahedral shape?
109.5
What are the electron pairs like in a tetrahedral shape?
- 4 bonding pairs
- 0 lone pairs
What are the bond angles in a trigonal bipyrimidal?
- 90
- 120
What are the electron pairs like in a trigonal bipyrimidal?
- 5 bonding pairs
- 0 lone pairs
What are the electron pairs like in an octahedral?
- 6 bonding pairs
- 0 lone pairs
What is the bond angle in an octahedral shape?
90
What are the bond angles in a See Saw?
- 120
- 90
What are the electron pairs like in a See Saw?
- 4 bonding pairs
- 1 lone pair
What are the electron pairs like in a square based pyramidal?
- 5 bonding pairs
- 1 lone pair
What is the bond angle in a square based pyramidal?
90
What is the bond angle in a square planar?
90
What are the electron pairs like in a square planar?
- 4 bonding pairs
- 2 lone pairs
How to work out enthalpy change if a question gives you mean bond enthalpies?
Reactants - products
Give three reasons why an experimental enthalpy change value may be different from a data book value?
- Heat loss to the surroundings (to the air)
- Heat energy absorbed by the apparatus (the stand + spirit burner etc..)
- incomplete combustion
Define the term standard enthalpy change of formation of a compound
The heat energy change when one mole of a substance is formed from its elements in their standard states under room temperature and standard pressure
What does a reaction being endothermic mean for the bonds?
Bonds are being broken
What does a reaction being exothermic mean for the bonds?
Bonds are being made
What is meant by lattice enthalpy?
The enthalpy change when one mole of a solid compound is formed from its constituent gaseous ions
What is meant by lattice enthalpy?
The enthalpy change when one mole of a solid compound is formed from its constituent gaseous ions
Why does the boiling point of halogens increase as you go down the group?
- the number of electrons on the atom increases
- therefore there are stronger London forces
- which require more energy to break
What is the standard state of bromine?
Liquid!
What is the standard state of nitrogen?
N•2(s)
Why is there a difference between the enthalpy change (data book value) of combustion, and the mean bond enthalpy?
- bond enthalpies refer to gaseous states, not liquid states
The molecular (parent) ion in a mass spectrum is..
A) the peak with the highest relative abundance
B) the peak with the highest relative charge
C) the peak produced by the most stable fragment
D) the peak with the highest mass to charge ratio
D) because the unfragmented ion is going to have the largest possible mass and charge
How do you work out where the mass spectrum peak would be given mass and charge?
Mass / charge
What does an OH bond show on a spectra graph?
A U-shaped curve at 3400 ish
What shows a C=O bond on a mass spectra graph?
A sharp peak between 1750-1630
How do you test for an alcohol functional group?
- mix with phosphorus pentachloride to produce white fumes
How do you test for an alkene functional group?
- mix with bromine water to decolorise from orange to colourless
Is the enthalpy of formation endothermic or exothermic?
Exothermic
Define the enthalpy change of formation
When one mole of solid ionic compound is formed from its gaseous constituent ions under standard conditions
What is the lattice enthalpy used for?
Ionic substances
Is the lattice enthalpy of dissociation typically exo or endothermic?
Endothermic
Define the lattice enthalpy of dissociation
The enthalpy change when 1 mole of solid ionic compound is dissociated into its gaseous constituent ions under standard conditions
When does the lattice enthalpy of dissociation increase?
With smaller ions and greater charge
Is the enthalpy of hydration normally positive or negative?
Normally negative
How does the enthalpy of hydration increase?
The attraction is stronger with smaller ions and greater charge
Define the enthalpy of hydration
The enthalpy change when one mole of gaseous ions are dissolved in water to form one mole of aqueous ions under standard conditions
Define the enthalpy of solution
The enthalpy change when one mole of ionic solid is dissolved in water to infinite dilution so that the ions no longer interact under standard conditions
How is covalent character formed?
Polarisation of anions by cations
Why can enthalpy of solution + hydration values be wrong?
It assumes a pure ionic character, when it may have covalent character
Define the term homologous
A family of compounds that have the same functional group but each member differs by a CH2 group
Why would the petroleum industry process straight chain alkanes into cyclic hydrocarbons?
Are more volatile and so have more efficient combustion
What is a condition required for nitrogen monoxide to be formed in an engine?
High temperatures (2500-4000) or a spark
What products are formed through the reaction of carbon monoxide and nitrogen monoxide in a catalytic converter?
Carbon dioxide and nitrogen gas
What substance can be used in a scrubber system in power station to remove sulfur-containing products + why it works?
- Calcium oxide
To neutralise SO2 as it is a base
Define reaction rate
The rate at which concentration of products or reactants changes per unit time
Why can’t c=c bonds freely rotate?
Because the overlap of the two 2P orbitals of the pi bond would break
What type of bonds does a c=c have?
Pi and sigma
What type of bonds does a c-c have?
Sigma
What temperature at minimum does a reaction need to be to form free radicals?
Above 450
What result occurs when silver nitrate is added to chloride ions?
White precipitate (AgCl)
What result occurs when silver nitrate is added to bromide ions?
Cream precipitate (AgBr)
What result occurs when silver nitrate is added to iodine ions?
Pale yellow precipitate (AgI)
Once silver nitrate had been added to chloride ions, and aqueous ammonia is added? What is its solubility in dilute and concentrated ammonia?
Dilute - soluble
Concentrated- N/A
Once silver nitrate had been added to bromide ions, and aqueous ammonia is added? What is its solubility in dilute and concentrated ammonia?
Dilute - insoluble
Concentrated - soluble
Once silver nitrate had been added to iodine ions, and aqueous ammonia is added? What is its solubility in dilute and concentrated ammonia?
Dilute - insoluble
Concentrated - insoluble
What is the result of adding sulfate VI (SO4) to barium chloride solution?
A white precipitate (BaSO4)
What is the result of adding sulfate IV (SO3) to barium chloride solution?
A white precipitate (BaSO3)
What is the result of adding carbonate (CO3) to barium chloride solution?
A white precipitate (BaCO3)
Once barium chloride solution has been added to sulfate (SO4), and dilute hydrochloric acid is added, what is the solubility of the precipitate?
The precipitate is insoluble
Once barium chloride solution has been added to sulfate (SO3) and dilute hydrochloric acid is added, what is the solubility of the precipitate?
The precipitate dissolves
Once barium chloride solution has been added to carbonate (CO3) and dilute hydrochloric acid is added, what is the solubility of the precipitate?
Precipitate dissolves
What takes place when concentrated sulfuric acid is added to chloride?
Steamy fumes
What takes place when concentrated sulfuric acid is added to bromide?
Steamy fumes + brown vapour
What takes place when concentrated sulfuric acid is added to iodide?
Steamy fumes, purple vapour, black solid or yellow solid
Describe the stages of reaction between NO and N2 with a platinum catalyst
- reactant absorbed onto the platinum surface
- reaction occurs on surface
- desorption of the product
How do you work out the enthalpy change of solution from hydration and lattice enthalpy? (Use XY as the compound)
Hydration of X + hydration of Y - lattice enthalpy change
