Chemistry Jan Synoptic Revision Flashcards
Give the symbol, including mass number, of the ion that reaches the detector first
Remember to include mass number (always the smallest one)
Remember to add the charge (question says ION, not atom)
Explain why the value for the O=O bond is not a mean value
Oxygen is the only substance that has an O=O bond, therefore cannot be averaged over a range of compounds
State and explain the effects on the pH of this buffer solution when a small amount of HCl is added
pH unchanged
H+ removed by A- forming HA/more HA formed. Less H+ means pH will not become more acidic
Enthalpy of combustion using Q=mcT
Always remember to add a minus to final answer as enthalpy of combustion is exothermic
State a condition to ensure that a primary amine is the major product
Excess ammonia
Define relative atomic mass
average mass of an atom of an element compared to 1/12th the mass of a C-12 atom
Why is Nitrogen B more likely to be protonated over Nitrogen A
Nitrogen B has alkyl groups surrounding it, which push electron density onto the lone pair on N, making it more readily available for protonation.
Nitrogen A has bases surrounding it. The lone pair on N becomes delocalised into the benzene ring.
State one example to be able to differentiate between ammonia and methylamine
Use a pH meter
Methylamine will have a higher pH as it is more basic. NH3 will have a lower pH.
Suggest the effect of air bubbles inside the burette would have on the amount of bromine water measured
Measured volume would be higher
Burette level will begin to fall before any liquid is released
Suggest another reason for students inaccuracy in results
Drop sizes of oil may vary
Outline how the student could improve this procedure to ensure that more consistent results are obtained when determining how many C=C bond are present in oil
Use a larger single volume of oil
Dissolve oil in organic solvent
Transfer to conical flask and add more solvent to fill up to 250cm3
Titrate 25cm3 from this flask
Suggest a possible reagent to go from NO2 to NH2
Addition of H2, H2 and NI catalyst under reduction
Or Sn catalyst and HCl
State what is meant by the term “mean bond enthalpy”
The enthalpy change when one mole of covalent bonds are broken to form gaseous ions, averaged over a range of compounds
What is a non-superimposable mirror image?
An enantiomer and its mirror image can be distinguished from each other
