F335 Flashcards
What oxidation states can group 5 elements have and why?
+ or -3: Three covalent bonds due to three unpaired electrons
+5: Dative covalent bond using lone pair as well
What is the bond between nitrogen atoms in N2?
Triple bond
Why does ammonia act as a base?
It has a lone pair so can form a dative covalent bond to form the ammonium ion
What is the name and appearance of NO?
Nitrogen(II) oxide
Colourless gas
What is the name and appearance of NO2?
Nitrogen(IV) oxide
Brown gas
What is the name and appearance of N2O?
Dinitrogen(I) oxide
Colourless gas
What is the equation for an equilibrium constant?
Concentration of products/Concentration of reactants
What happens to the equilibrium constant if the concentrations are changed?
Nothing
What happens to the equilibrium constant if the pressure is changed?
Nothing
What happens to the equilibrium constant if the temperature is changed?
If exothermic, an increase in temperature results in a decrease in Kc
What happens to the equilibrium constant if a catalyst is used?
Nothing
What are the key features of organic farming?
Little artificial fertilisers and pesticides used
Emphasis on soil health
How do farmers ensure soil is organically kept fertile and contains enough nutrients?
Crop rotations
Growing crops that are ploughed back into the soil
Using composts and manures
Applying certain fertilisers and nutrients
What is the catalyst for the Haber process?
Finely divided iron
What is the reaction in the Haber process?
Nitrogen gas + Hydrogen -> Ammonia
450 degrees
What is added to soil to increase pH?
Lime
Why is DDT banned from being used as a pesticide?
Remain in soil
Build up in food chain
What organic measures are used to control pests?
Crop rotation Physical barriers Weeding Limited use of certain pesticides Growing companion plants close by
What is a chromophore?
An extended delocalised electron system
Why do double bonds absorb light in the visible region?
Their electrons are more spread out so need less energy to excite
Why do compounds containing transition metals appear coloured?
The d orbitals are split into two groups of different energy levels
What is a paint made of?
The pigment
The liquid that carries the pigment
What is a reflectance spectrum?
White light shone on material, colours missing are the ones absorbed
How does an absorption spectrum work?
Shine white light on solution of sample
Measure intensity of absorption for each wavelength
How is an absorption spectrum interpreted?
Wavelength of radiation absorbed - Determines colour
Shape of absorption band - Shade of colour seen
Width of absorption band - Purity of colour seen
What is a triglyceride made of?
Glycerol
Three carboxylic acids
Ester bonds
What is the name of a benzene ring with a chlorine attached?
Chlorobenzene
What is the name of a benzene ring with an NO2 attached?
Nitrobenzene
What is the name of a benzene ring with a carboxyl group attached?
Benzoic acid
What is the name of a benzene ring with an aldehyde group attached?
Benzaldehyde
What is the name of a benzene ring with a methanol attached?
Benzyl alcohol
What is the name of a benzene ring with an -OH attached?
Phenol
What is the name of a benzene ring with an -NH2 attached?
Phenylamine
What are the reagents, conditions and products of bromination of benzene?
Reactant: Bromine
Catalyst: FeBr3 - Iron(III) bromide
Product: Bromobenzene
What are the reagents, conditions and products of nitration of benzene?
Reactant: HNO3
Catalyst: Concentrated sulphuric acid
Conditions: Below 55C
Product: Nitrobenzene
What are the reagents, conditions and products of sulfonation of benzene?
Reactant: Sulphuric acid
Reflux
Product: Benzenesulfonic acid
What are the reagents, conditions and products of chlorination of benzene?
Reactants: C-Cl
Catalyst: AlCl3
Product: Chlorobenzene
What are the reagents and conditions of a Friedel-Crafts reaction?
AlCl3
Reflux
How are azo compounds formed?
Coupling reaction
Between diazonium salt and a coupling agent
How are diazonium salts prepared?
NaNO2 reacted with HCl to form Sodium Chloride and HNO2 (Nitrous acid)
Phenylamine reacted with nitrous acid to form benzenediazonium ion
What colour is the compound formed when a diazonium ion reacts with phenol?
Yellow-orange
What colour is the compound formed when a diazonium ion reacts with naphthalen-2-ol?
Red
What colour is the compound formed when a diazonium ion reacts with phenylamine?
Yellow
What are the two most abundant ions in salt water?
Sodium and chloride
What is a lattice enthalpy?
The strength of the ionic attractions in a lattice
What is the enthalpy change in forming an ionic lattice?
Exothermic
Negative
What causes a more negative lattice enthalpy and why?
Increased ionic charge - Attract more strongly
Decreased ionic radii - Closer together so stronger attractions
What does it mean when the ions in a solution are hydrated?
They have water molecules bound to them
What is the enthalpy of hydration?
The strength of the attractions between ions and water molecules
What does the symbol (aq) mean?
Water when it is acting as a solvent
What causes the most exothermic enthalpy’s of hydration?
Greatest charge
Smallest radii
What is the enthalpy change of solution?
Enthalpy of hydration cation + enthalpy of hydration for anion - lattice enthalpy
What is the entropy change when a solute dissolves?
Increase in entropy
What are cloud condensation nuclei?
Small particles in the atmosphere that bind water molecules together and so encourage the formation of clouds
How do you calculate pH?
-log(Concentration of hydrogen ions)
How is concentration of hydrogen ions found for a strong acid?
Since reaction goes to near completion, equal to moles of acid put in
What assumptions are made about weak acids?
Concentration of hydrogen = Concentration of A-
Amount of HA at equilibrium = Amount of HA put in
What is the equilibrium constant equation for a weak acid?
Ka = Concentration of hydrogen squared / Concentration of HA
How is concentration of hydrogen ions found for a weak acid?
Rearranging of the equilibrium constant equation
How is strength of an acid shown?
The greater its Ka value is or the smaller its pKa value is, the greater its strength
What are the differences between strong and weak acids?
Strong acids have lower pH for same concentration
Strong acid has higher electrical conductivity for equivalent concentration
Strong acid has faster reaction rate for equal concentration
What are the three ways to reduce the build-up of carbon dioxide in the atmosphere?
Alternative fuels
Use fossil fuels more effectively
Capture and store carbon dioxide
What are the four suggested methods of capturing and storing carbon dioxide?
Turning it into useful products
Growing more trees
Storing in deep trenches on the sea floor
Injecting the gas onto the sea floor
What is a buffer solution?
A solution which can resist changes in pH despite the addition of acid or alkali
What are buffer solutions usually made from?
A weak acid and one of its salts
OR
A weak base and one of its salts
What assumptions are made about species present at equilibrium for buffer solutions?
All the A- ions come from the salt
Almost all the HA molecules remain unchanged
What can the equilibrium equation for a buffer solution be written as?
Ka = Concentration of hydrogen ions * (Concentration of salt / Concentration of acid)
How can fine and coarse tuning of a buffers pH be done?
Coarse tuning - Modifying the value of Ka
Fine tuning - Changing the ratio of concentrations of salt and acid
What are the equations for the carbon dioxide equilibria in water?
CO2(g)CO(aq)
CO2(aq) + H2O(l) H+(aq) + (HCO3)-(aq)
(HCO3)-(aq) H+(aq) + (CO3)2-(aq)
What is the overall equation for the carbon dioxide equilibria?
CO2(g) + H2O(l) 2H+(aq) + (CO3)2-(aq)
What is specific heat capacity?
A measure of how much energy is required to warm something up
What are the three forms of kinetic energy molecules can possess?
Translation
Rotation
Vibration
What is entropy?
A measure of the number of ways of arranging molecules and distributing their quanta of energy
What substances have higher entropies?
Ones with heavier atoms and more atoms
How is the entropy change for the surroundings calculated?
- ## Enthalpy changeTemperature in Kelvin
How is the total entropy change calculated?
Entropy change for the system + Entropy change for the surroundings
What must the entropy change be for reactions to occur?
Positive
What are spontaneous changes?
Changes which occur of their own accord as the total entropy change is positive
What is the entropy change for a reaction?
Total entropy change for the products - Total entropy change for the reactants
What is the entropy change for an equilibrium to occur?
Zero
Why does waters density decrease when frozen?
It expands
What two areas are focused on when designing a new medicine?
Developing a biological understanding of the condition
Finding a lead compound to use
What does n.m.r. look at?
The different chemical environments hydrogen nuclei are in
How is splitting determined?
One more peak than the number of adjacent hydrogen nuclei
What are the three stages in preparing an organic compound?
Reaction
Extraction of product
Purification of product
What is a target molecule?
The desired compound
What is retrosynthetic analysis?
The process of working backwards from the target molecule in order to devise a synthetic route
What is a disconnection?
An imagined breaking of a bond to suggest two fragments that could be reacted together to get the target molecule
What is a synthon?
An idealised fragment resulting from a disconnection
What is a synthetic equivalent?
The actual compounds used that function as synthons
How are penicillins normally made?
Adding side-chains to 6-APA
