past papers Flashcards
what order do orbitals fill in according to the aufbau principle
1s 2s 2p 3s 3p 4s 3d 4p
how can you determine the shape of a molecule from its molecular formula
using that equation to work out how many electron pairs there are (bonding and non bonding)
how can you determine the conductivity of a solution when something has been added to water
look at the dissociation of ions because conductivity is just the movement of ions
does E have to be positive or negative for a reaction to be feasible
positive
why is ammonia a good nucleophile
has a lone pair and is attracted to centres of positive charge
what causes the separation of the ions in mass spectroscopy
a magnetic field
what is produced by reacting benzene with nitric or sulfuric acid
nitrobenzene
give an example of an aldehyde that would produce a primary alcohol
methanal
do ethers show hydrogen bonding
no
how do you work out the splitting pattern of a hydrogen atom in nmr
the number of peaks is equal to the number of adjacent hydrogen atoms - if it is attached to the same carbon it is not adjacent
when would volumetric analysis be more efficient than gravimetric analysis
when there are smaller quantities, as titrations are more suited to these
why would the optical activity of a substance decrease over time
because a racemic mixture is forming
suggest a suitable reagent for converting ketone carbonyl group to hydroxyl group
lithium aluminium hydride
what are the units for k in a zero order reaction
mol l-1 s-1
what are the units for k in a first order reaction
s-1
what are the units for k in a second order reaction
mol-1 l s-1
what are the units for k in a third order reaction
mol-2 l2 s-1
what is the value of l in an s orbital
0
what is the name given to chloride in a ligand if it is negative
chloro
what is the name given to cyanide in a negative ligand
cyano
what is the name given to hydroxide in a negative ligand
hydroxo
what is the name for ammonia when it is a ligand
ammine
what is the name for water as a ligand
aqua
what is the name for carbon monoxide in a ligand
carbonyl
what is the name for nitrate ion when it is in a ligand
nitrito
what is the name for the complex ion containing cobalt when there is an overall negative charge
cobaltate
what is the name for the complex ion containing iron when there is an overall negative charge
ferrate
what is the name for the complex ion containing copper when there is an overall negative charge
cuprate
if something has a low wavelength, its frequency is…
high
explain what is thought to take place when carbon atoms form four equivalent single bonds in methane
a combining of one s orbital and three p orbitals in what is known as sp3 hybridisation to form four degenerate hybrid orbitals
what is the reaction type of forming a haloalkane from an alcohol
substitution
give two reasons to explain why a reaction is more likely to take place via an Sn1 mechanism rather than an Sn2 mechanism
steric hinderance can prevent 5 numbered intermediate forming in the sn2 mechanism
the carbocation intermediate is stabilised by the inductive effect from the two alkyl groups in the intermediate
suggest why two isomers may be formed in an sn1 mechanism
the attacking group can attack from either side of the carbocation making both of the optical isomers
what is a reagent that could be used to form methyl benzene from benzene
bromomethane
what is a catalysis that could be used to form methyl benzene from benzene
aluminium chloride
why is benzene stable
the delocalisation of the electrons within the ring gives stability
which reagent could be used to carry out synthesis of an alcohol from an aldeyhde
lithium aluminium hydride
a solution of hypochlorous acid was titrated with sodium hydroxide solution. the solution at the end point was alkaline. explain fully why the solution was alkaline at the end point.
the hydrogen ions are removed by the conjugate base from the water equilibrium, and the equilibrium moves to the right.
suggest why the entropy change for liquid water to gaseous water is different to the same state change of carbon chloride
the entropy of liquid waer is much lower than that of carbon chloride and so there is more order - this is due to the hydrogen bonds.
the change from an ordered system of water to free molucules therefore results in a greater change in entropy than in carbon chloride
describe how separate samples of two enantiomer could be distinguished
their plane polarised light will be rotated in equal but opposite directions
state how sp2 hybridisation arises
one s orbital and two p orbitals combine to make three degenerate sp2 hybrid orbitals
why is it necessary to protect an amine group during synthesis
because the nitrogen of the amine group is a nucleophile and could also react
why is ethanol a suitable solvent for recrystallisation
the reactant is completely soluble in ethanol at high temperatures and only slightly soluble at low temperatures, which allows the formation of pure crystals when the solvent is cooled down.
state an effect on the impurities within a substance on the melting point
the melting point will have a wider range
why do impurities lead to a different melting point
there are weaker intermolecular forces in the pure substance compared to the impure one
what is the name of the reaction when an alcohol is converted to an ether
condensation
why can an integration curve be used to confirm if a sample is what it is meant to be
the ratio can agree with the ratio of hydrogen atoms in each environment
what is meant by a monodentate ligand
a ligand that forms one dative covalent bond to a central metal ion
explain the benefit of selling a drug with an equal mix of both enantiomers
it is cheaper to have a racemic mixture because you won’t have to separate the enantiomers
describe how the technique of colorimetry can be used to determine the concentration of permangenate ions
- several solutions of accurate concentration of the substance are made up
- absorbance of each one is measured
- calibration curve of concentration vs absorbance is drawn
- the concentration of the solution with an unknown concentration of the substance can be determined from the calibration graph and its absorbance
why is a reaction likely to continue
if the free energy is below zero and therefore remains feasible
why are tertiary haloalkanes more suitable to use for nucleophilic substitution than primary or secondary
there is higher steric hindrance, so the carbocation is more stable
how would you calculate the PH of an acid with a known concentration
using the formula that uses the literal concentration value
why would a transition metal complex appear coloured
the ligand splits d orbitals, making them no longer degenerate.
energy corresponding to the wavelengths in the visible spectrum is absorbed, and this promotes electrons
which type of bonds do sp3 hybridisation contain
only sigma
how many sigma bonds are there between C-C
1
how many pi bonds are there between C-C
0
how many sigma bonds are there between C=C
1
how many pi bonds are there between C=C
1
how many sigma bonds are there between C-H
1
how many pi bonds are there between C-H
0
how many sigma bonds are there between N=C
1
how many pi bonds are there between N=C
1
how many sigma bonds are there between N-C
1
how many pi bonds are there between N-C
0
suggest a reason why bond angle is less in POCl3 than the bond angle in PCl4
there is stronger repulsion from the double bond
what are tetradentate ligands
ligands that bind four donor atoms to a central atom to form a coordination complex
why may something have a geometric isomer
restricted rotation due to double bond or ring structure
how may a drug bind to the active site
the enzyme active site binds to parts of the molecule that have the ability to form hydrogen bonds
do minor products have more or less stable carbocations
less stable carbocation.
suggest a reagent for hydrolysing a nitrile into a carboxylic acid
any dilute acid, like hydrochloric acid
what is the shape of a molecule with 2 bonding and 0 lone
linear
what is the shape of a molecule with 3 bonding and 0 lone
trigonal planar
what is the shape of a molecule with 4 bonding and 0 lone
tetrahedral
what is the shape of a molecule with 2 bnding and 0 lone
non linear
what is the shape of a molecule with 3 bonding and 1 lone
pyramidal
what is the shape of a molecule with 5 bonding and 0 lone
trigonal bipyramidal
what is the shape of a molecule with 6 bonding and 0 lone
octahedral
what is the shape of a molecule with 4 bonding and 2 lone
square planar
what happens to the value of entropy if a molecule because more ordered
it decreases
how many pi bonds are there between carbon and nitrogen
2
explain the effect of infrared radiation has on the bonds within molecules and how this allows different functional groups to be identified
the ir radiation makes the bonds in the molecule vibrate. different bonds in the functional groups absorb different wavelengths of light
what do group 1 metals react with to form alkoxides
alcohols
how do you order the ligands in the naming
alphabetically
what is the prefix if there is only one ligand
mono
what is the reaction name when reacting chloropropane with benzene
substitution apparently
why would a back titration be necessary
because the substance is insoluble
what are some analytical techniques that can be used to determine the concentration of metal ions in a compound
complexometric titration
absorption spectroscopy
precipitation
how are nitriles formed
transition state
which mechanism do primary haloalkanes react by
Sn2
which mechanism do secondary haloalkanes react by
Sn2
which mechanism do tertiary haloalkanes react by
Sn1
why should the pH of a buffer solution remain constant when a small volume of water is added
because the acid and the salt are diluted by the same amount
how could the alcohol and carboxylic acid be separated after hydrolysis of an ester
distillation
what is the electrophile in a hydrogen halide
the positively charged hydrogen
why is an aqueous solution of sodium benzoate alkaline
the ion from the salt removes hydrogen ions from the water (because its aqueous there is water)
this results in excess OH- ions from the water equilibrium
do neon discharge lamps absorb radiation
no
how do you determine if an indicator is suitable for determining the equivalence point
its pH range is within the vertical region on the graph
what type of reaction is condensation
exothermic
what type of reaction is neutralisation
exothermic
which pH do amines have
an alkaline one
what determines the type of structure adopted by a particular ionic compound
radius ratio of the ions
what does the line on the graph for rate over concentration for a zero order reaction look like
a horizontal straight line
what does the line on the graph for rate over concentration for a first order reaction look like
a straight line with a positive correlation as you increase the concentration
what does the line on the graph for rate over concentration for a second order reaction look like
a curved line with a positive correlation as you increase the concentration
what does the line on the graph for concentration over time look for a zero order reaction
a straiht line with a negative correlation as the time increases
what does the line on the graph for concentration over time look like for a first order reaction
a curved line with a negative correlation that is quite a wide range of correlation
what does the line on the graph for concentration over time look like for a second order reaction
a curved line with a negative correlation that has a much steeper correlation than in first order
name the gas produced when water reacts with lithium aluminium hydride
hydrogen
what should be added to a flask when heating under reflux
antibumping granules
why are antibumping granules used
to prevent chemicals jumping up the reflux apparatus
which technique could be used to both purify and identify a compound
distillation
the absorption of radiation in the radiofrequency region causes proton nuclei to adopt a high energy state aligned against a strong magnetic field. explain how this leads to peaks in an nmr spectrum corresponding to different proton environments
the hydrogen nuclei flip to low energy and align with the magnetic field.
the different hydrogen environments have different energy gaps between high and low states
what causes the splitting of d orbitals when a ligand binds
the repulsion from the lone pairs on the ligand
what is meant by the term nucleophile
negatively charged ions that are electron rich
why could two different drugs bind to the same receptor
they have the same structural fragment that binds to the receptor
