AQA A-LEVEL CHEMISTRY TOPIC 1 - EXAM
QUESTIONS WITH COMPLETE SOLUTIONS.
Calculate the relative atomic mass...
Explain why the value you have calculated is slightly
different from the relative atomic mass given in the
periodic table. - correct answer - The Ar in the periodic
table takes into account the other isotopes.
Deduce which of Na+ and Mg 2+ is the smaller ion.
Explain your answer. (2 marks) - correct answer - - Mg
2+ is the smaller ion.
- they both have the same number of electrons but Mg
2+ has more protons
Define the term mass number of an atom - correct
answer - number of protons plus number of neutrons in
the nucleus
Describe how ions are formed in a time of flight mass
spectrometer. (2 marks) - correct answer - - a high
voltage is applied to a sample in a polar solvent
- the atoms gain protons and become positive ions
, Explain how ions are accelerated, detected and have their
abundance determined in a TOF mass spectrometer. (3
marks) - correct answer - - accelerated towards a
negatively charged plate
- detected by gaining electrons
- abundance determined by the size of the current flowing
in the detector
Explain how the detector in a mass spectrometer enables
the abundance of an isotope to be measured. - correct
answer - - ions hit the detector and cause a current to
flow
- bigger current = higher abundance
Explain why it is necessary to ionise molecules when
measuring their mass in a TOF mass spectrometer. (2
marks) - correct answer - - only ions will be accelerated
by an electric field
- also so that they produce a current when they hit the
detector
Explain why sodium has a lower melting point than
magnesium. - correct answer - - sodium has fewer
protons
- smaller attraction between nucleus and delocalised
electrons
QUESTIONS WITH COMPLETE SOLUTIONS.
Calculate the relative atomic mass...
Explain why the value you have calculated is slightly
different from the relative atomic mass given in the
periodic table. - correct answer - The Ar in the periodic
table takes into account the other isotopes.
Deduce which of Na+ and Mg 2+ is the smaller ion.
Explain your answer. (2 marks) - correct answer - - Mg
2+ is the smaller ion.
- they both have the same number of electrons but Mg
2+ has more protons
Define the term mass number of an atom - correct
answer - number of protons plus number of neutrons in
the nucleus
Describe how ions are formed in a time of flight mass
spectrometer. (2 marks) - correct answer - - a high
voltage is applied to a sample in a polar solvent
- the atoms gain protons and become positive ions
, Explain how ions are accelerated, detected and have their
abundance determined in a TOF mass spectrometer. (3
marks) - correct answer - - accelerated towards a
negatively charged plate
- detected by gaining electrons
- abundance determined by the size of the current flowing
in the detector
Explain how the detector in a mass spectrometer enables
the abundance of an isotope to be measured. - correct
answer - - ions hit the detector and cause a current to
flow
- bigger current = higher abundance
Explain why it is necessary to ionise molecules when
measuring their mass in a TOF mass spectrometer. (2
marks) - correct answer - - only ions will be accelerated
by an electric field
- also so that they produce a current when they hit the
detector
Explain why sodium has a lower melting point than
magnesium. - correct answer - - sodium has fewer
protons
- smaller attraction between nucleus and delocalised
electrons
