Chem 2a Q Flashcards
Explain why an incorrect value for the number of moles of iron(II) chloride would have been obtained if the original solution had been titrated with potassium manganate(VII)
KMnO4 would oxidise Cl- as well as Fe2+, so titration value would be too large.
In what way does the NH3 behave as a Brønsted–Lowry base?
Proton acceptor
In what way does the NH3 behave as a Lewis base?
Electron pair donor
State and explain the effect of a catalyst on rate in a reversible reaction.
- Increases the rate at which eqm .is reached
- Catalyst provides alternative reaction route w/ lower Ea
- More particles have this Ea so the reaction is faster
State and explain the effect of a catalyst on eqm. yield in a reversible reaction.
- No effect on eqm yield
- Forward & backward reaction rate speeded up equally.
Reactions for Fe2+ as a homogenous catalyst for the reaction of I- and S2O8(2-).
2Fe^(2+) + S2O8^(2–) –> 2SO4^(2–) + 2Fe^(3+)
2Fe^(3+) + 2I– –> 2Fe^(2+) + I2
Ligand
Electron pair donor
Complex ion
Central metal atom or ion surrounded by ligands attached by coordinate bonds
Co ordinate number
The number of coordinate bonds made by a metal atom or ion to the ligands
A ligand substitution reaction which occurs with no change in the co-ordination number but a change in the charge on the complex ion.
[Fe(H2O)6]^(2+) + 3C2O4^(2–) –> [Fe(C2O4)3]^(4–) + 6H2O
Explain why the pH of a solution of iron(II) chloride is higher than that of a solution of iron(III) chloride of the same concentration.
The charge density on Fe2+ is less than on Fe3+ so it is less polarising to the water ligands and fewer H+ ions are released
State the origin of the colour of transition-metal complexes
Movement of electrons within the d sub-level orbitals
Give three changes to a transition-metal complex which result in a change in colour
Oxidation state
Coordination number
Ligand substitution
Coordinate bond
Where one of the atoms involved donates both electrons to the shared pair
Bidentate ligand
One which uses two lone pairs to link onto a metal atom or ion.
Suggest why the enthalpy change for a reaction may be close to zero
Because the bonds formed are approximately the same strength as those broken
Zwitterion in acidic conditions
NH2 becomes NH3+
COOH becomes COO-
Why can Vanadium(III) catalyse the reaction between S2O8^(2-) and I- but Mg(II) can’t?
Vanadium(III) can be oxidised to a higher state whereas Mg(II) cannot.
Why is the complex formed when a copper aq ion reacts with EDTA^(4-) more stable than the Cu aq ion?
Large increase in entropy as 2 particles form 7 - increases stability.
Reagent needed to carry out
CrO4^(2–) (aq) → Cr2O7^(2–) (aq)
Strong acid like HCl
Reagent needed to carry out
VO^(2+) (aq) → [V(H2O)6]^(2+) (aq)
Zn metal and HCl
Reagent needed to carry out
[Ag(NH3)2]^(+)(aq) → Ag(s)
Aldehyde
CH3CHO
chelate
A central metal ion complexed with a multidentate ligand forming a more stable complex
Give one reason why sulphur dioxide gas may be found in the exhaust gases of cars.
Sulphur present in petrol
Give one reason why sulphur dioxide is considered to be a pollutant.
Gives acid rain
3 characteristics of a homologous series
- Can be displayed by a general formula
- Vary by constant amount
- Show a gradation in properties
Molecular formula
Actual number of each type of atom in one molecule of a substance
Cracking
T - 400-900˚C
The breaking of a long alkane chain into smaller alkanes and alkenes
What is a fraction
A part of crude oil with a specific boiling range
Economic value of cracking
Use up low demand fractions/Produce commercially favoured fractions like petrol
functional group isomerism.
Where the atoms of one functional group can be rearranged to produce one or more other functional groups.
Empirical formula
Simplest whole number ratio of atoms in a compound
Structural isomer
Same molecular formula but different structural formulae
Position isomer
Where a particular functional group could be placed in more than one position in the carbon chain
Stereoisomers
Same molecular and structural formulae, different spatial arrangement.
Identify the type of reactive intermediates formed during thermal cracking and explain how they are produced.
Free-radicals
the C-C bonds split homolytically
Why are polymers solid at room temperature?
the long polymer chains are connected by very many van der Waal’s forces
these take a lot of energy to separate - high m.p.
Name the type of polymerisation which occurs when ethene is converted into poly(ethene).
Addition
Explain why ethene is able to react with bromine in an electrophillic addition reaction, given that bromine molecules are non-polar.
Induced dipole in the bromine molecule
attack by δ+ on one Br
Conditions for nucleophillic substitution
Aqueous
Warm
Condtions and reagent for an elimination reaction
Alcoholic solution
KOH
Why is an elimination reaction of CH3CH2Br with OH- not used to produce ethene in industry
Alternative reaction produces ethanol and reduces yield
State four essential conditions for the conversion of glucose into ethanol
Yeast
temp. around 37˚C
Water
Anaerobic conditions
Identify a catalyst which could be used in the acid-catalysed dehydration of ethanol
H2SO4
Give one advantage of the use of propanoyl chloride instead of propanoic acid in the laboratory preparation of methyl propanoate from methanol.
Faster reaction
better yield
Give one advantage of the use of propanoic anhydride instead of propanoyl chloride in the industrial manufacture of methyl propanoate from methanol.
Cheaper reagent
Less toxic
Less violent reaction
Safe
Conditions for reducing aldehyde/ketone
NaBH4
Water
Conditions for esterification
Aldehyde + ketone
conc. H2SO4
In the industrial manufacture of aspirin, ethanoic anhydride is used as an acylating agent rather than ethanoyl chloride. Give two reasons why ethanoic anhydride is preferred.
Cheaper reagent
Less toxic
Less violent reaction
Safer
Reaction to distinguish between ethanoic anhydride and ethanoyl chloride
Add water
ethanoic anhydride - no initial reaction
ethanoyl chloride - violent exothermic reaction
