Exam questions physical chemistry Flashcards
State and explain the trend in the first ionisation energies of the elements in Group
2 from magnesium to barium.
- decrease in ionization energy
- ions have more energy levels
- so weaker attraction of ion to lost electron
State the element in Period 3 that has the highest melting point.
Explain your answer.
- silicon is the element with the highest melting point
- has covalent bonds
-which are very strong and require a lot of energy to break ( covalent bonds are the strongest of all three bonds)
Write an equation to show the process that occurs when the second ionisation
energy of boron is measured. Include state symbols in your equation.
B + - e …> B 2+
Explain why the second ionisation of boron is higher than the first
electron being removed from positive ion requires more energy ( 1 mark)
background detail not incl in MS
-overall positive charge means that electrons are more attracted to nucleus so harder to tug them away from ion
State the block in the periodc table that nickel is in
D block
Give electron config of ni2+ ion
1s2 2s2 2p6 3s2 3p6 4s0 3d8
- From Sc on, the 3d orbitals are actually lower in energy than the 4s orbital, which means that electrons enter the 3d orbitals first.
What can react with both HCL and SO2
water or a base ie NAOH or CaO
An acidified solution of NH4VO3 reacts with zinc.
Explain how observations from this reaction show that vanadium exists in at least
two different oxidation states.
Two different colours of solution are observed
Because each colour is due to vanadium in a different oxidation state
2 marks
Predict whether the atomic radius of 124Te is larger than, smaller than or the same as
the atomic radius of 130Te
Explain your answer
They would be the same
each isotope has same number of protons and electrons ( only neutrons changes)
A TOF mass spectrometer can be used to determine the relative molecular mass of
molecular substances.
Explain why it is necessary to ionise molecules when measuring their mass in a
TOF mass spectrometer.
- atoms wouldn’t be accelerated by an electric field
- only ions would generate a current when they hit the detector
The mass spectrum of tellurium also has a small peak at m / z = 64
Explain the existence of this peak
2 electrons removed
From 128 (Te)
background info not on MS
- therefore m/z ratio halves because a 2 + Te ion has been formed
Explain why the boiling points increase from H2S to H2Te ( 2 marks)
- atoms/ molecules getting larger ( more shells) because of Te’s pos in the periodic table compared to S
- so the attraction ( IMF) between H and Te is stronger
Describe the bonding in a metal
( 2 marks)
- cations ( metal atoms have lost electrons)
- have a strong attraction to the sea of delocalized electrons.
Why do both graphite and diamond have very high melting points?
( 3 marks)
- carbon atoms in both diamond and graphite are held together by covalent bonds
- covalent bonds are very strong due to the strong force of attraction between the nucleus and shared electron pair
- lots of covalent bonds to break because diamonds and graph are macromolecules.
Why is graphite a good conductor of electricity ( 1 mark)
- graphite contains delocalised electrons to carry the electric charge
