CHEM4 Revision Cards
Questions taken straight from exam papers-common questions
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- Created by: James Gillie
- Created on: 21-12-12 16:54
What affects the time taken for a substance to move down the column in chromatography?
It depends on the balance between the solubility of each substance in the mobile phase (the solvent) and its retention in the stationary phase (the powder)
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How are the substances separated as they travel through the gas liquid column?
Depending on their affinity (attraction) for the stationary and mobile phases
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What is the method for calculating the pH of a buffer solution?
1) Calculate the moles of OH- 2) Calculate the moles of acid 3) Calculate the moles of acid left-excess 4) Moles X- in buffer = OH- 5) Conc H+ = Ka x moles acid left / OH- left in buffer 6) pH = -log(H+)
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How do you get NO2+? What is its equation?
H2SO4 + HNO3 --> NO2+ + H2SO4- + H2O
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What name is given to NO2+ reacting with benzene?
Nucleophilic substitution
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What is the difference in biodegradability between kevlar and polymerised alkenes? Give reference to the bonding in the polymers
1) Kevlar is biodegradable 2) Kevlar has polar bonds 3) Can be hydrolysed/attacked by nucleophiles/acids/bases/enzymes 4) Polyaklanes are non-polar/have non polar-bonds
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What titration's is phenolphthalein used in + colour change?
1) Strong - Strong 2) Weak acid - Strong alkali 3) Pink --> Colourless
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What is the IUPAC name for glycerol?
Propan-1,2,3-triol
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What is the solvent used in H-NMR?
1) CCl4 2) CDCl3 3) C6D6
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By considering their optical activity - explain how these products cannot be distinguished between?
1) Product Q is a racemic mixture 2) Hence equal amounts of each enantomer 3) Racemic mixture is inactive 4) Product R is inactive-no chiral centre
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What are the benefits of using anhydides over -oyl chlorides?
1) Less corrosive 2) Less vulnerable to hydrolysis 3) Less dangerous to use 4) Less violent 5) No toxic HCl produced 6) Less volatile
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What is the integration ratio?
It is the relative intensity of the peaks on the speectra e.g. 3:2:2:3
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What is the equation for Kc?
Products / Reactants (look at the stockiometry)
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Does Kc vary with temperature or pressure?
Kc varies with temperature not with pressure
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What is retention time?
It is the time taken for a substance to pass through the column
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What are the uses of a quaternary alkylammonium salt?
1) Cationic surfactant 2) Bactericide 3) Detergents 4) Fabric softener
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Why is butylamine a stronger base than ammonia >?
1) Lone pair on nitrogen 2) R group increases electron density 3) Has positive inductive effect 4) Makes the lone pair more available on the nitrogen
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Why is major product more likely to be produced in a reaction?
1) Major product is more stable as its carbocation 2) There is less sterickhinderence
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1) Aldehyde + NaBH4 -->? 2) Aldehyde + Fehlings -->? 3) Aldehyde + HCN -->?
1) Primary alcohol 2) Carboxylic acid 3) Secondary alcohol
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Why is phenylamine a weaker base than ethylamine?
1) Lone pair on N is less available 2) Due to delocalisation
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Hydrogen atoms with a large chemical shift are said to be...?
Deshielded
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Hydrogen atoms with a small chemical shift are said to be...?
Shielded
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How is splitting calculated?
The way in which each peak is split depends on the total number of hydrogen atoms on adjacent carbon atoms
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For values of n 0-6, what will be their type of peak?
0) Singlet 1) Doblet 2) Triplet 3) Quartet 4) Quintet 5) Sextet 6) Septet
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What is the standard used in H NMR?
TMS - it has 12 identical hydrogen atoms which will produce one large peak which is used as the standard
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Why is TMS used as a standard?
1) It produces one single large peak-as it has 12 identical peaks 2) The H atoms are well shielded-as the Si is an electropositive atom, releasing electron density onto the H atoms 3) It is cheap and non-toxic
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Other cards in this set
Card 2
Front
How are the substances separated as they travel through the gas liquid column?
Back
Depending on their affinity (attraction) for the stationary and mobile phases
Card 3
Front
What is the method for calculating the pH of a buffer solution?
Back
Card 4
Front
How do you get NO2+? What is its equation?
Back
Card 5
Front
What name is given to NO2+ reacting with benzene?
Back
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