PAPER 1 worded questions Flashcards
(42 cards)
Suggest what might cause the relative atomic mass of this sample to be
different from the relative atomic mass given in the Periodic Table
(1 mark)
Other isotopes present / some isotopes absent / different abundances of
isotopes
Btw isotopes is UNDERLINED
State the m / z value of the ions that produce the biggest current at the detector
when the spectrum in the graph is recorded.
Give a reason for your answer. (2 marks)
Mark 1: say the one with the biggest line on the graph
Mark 2: highest realative abundence
The mass spectrum of tellurium also has a small peak at m / z = 64
Explain the existence of this peak. (2 marks)
Mark 1: 2+ ion formed / 2 electrons removed
Mark 2: due to terleium 128
Due to 128Te2+ = 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. (2 marks)
Mark 1: the same
Mark 2:
(Each isotope has the) same number of protons / same nuclear charge and
same number of electrons / electronic configuration
Describe how ions are formed in a time of flight (TOF) mass spectrometer. (2 marks)
Electrospray
Mark 1: A high voltage is applied to a sample in a polar solvent
Mark 2: the sample molecule, M, gains a proton forming MH+
or electron impact
Mark 1: the sample is bombarded by high energy electrons
Mark 2: the sample molecule loses an electron forming M+
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. (2 marks)
1) ions, not molecules, will interact with and be accelerated by an electric field
2) Only ions will create a current when hitting the detector
In a mass spectrometer, the isotopes of an element are separated.
Two measurements for each isotope are recorded on the mass spectrum.
State the two measurements that are recorded for each isotope. (2 marks)
1) M/Z
2) relative abundence
Define the term relative atomic mass
Average / mean mass of 1 atom (of an element)
1/12 mass of one atom of 12C
In a mass spectrometer, the relative abundance of each isotope is proportional to the current generated by that isotope at the detector.
Explain how this current is generated. 2 marks
Electron(s) transferred / flow (at the detector)
M1 must refer to electron flow at the detector.
M2 : (From detector / plate) to the (+) ion
Outline how the TOF mass spectrometer is able to separate these two species to give two peaks. ( 4 marks)
- Positive ions are accelerated by an electric field
- To a constant kinetic energy
- The positive ions with m / z of 104 have the same kinetic energy as those with m / z of 118 and move faster
- Therefore, ions with m / z of 104 arrive at the detector first
Explain the meaning of the term first ionisation of an atom.
2 marks
Enthalpy change is required to remove 1 mole of electrons from 1 mole of a gaseous ions
Explain what is meant by the term electronegativity
ability (or power) of an atom to attract electron density
(or electrons or ‑ ve charge) (1)
in a covalent bond (1)
Suggest how a student doing this experiment could check that all the water had been removed
Reheat it
and check if the mass is constant
Describe the structure of and bonding in graphite and explain why the melting point of graphite is very high
Layers of (C atoms)
Connected by covalent bonds within each layer
Van der Waals forces/IMF between layers/weak forces between layers
Many/strong covalent bonds need to be broken
Suggest one property of an impurity that would cause the calculated mass of FeSO4.7H2O in X to be greater than the actual mass of X.
Explain your answer
Impurity is a) reducing agent / reacts with dichromate / impurity is a version of
1
1
FeSO
4
with fewer than 7 waters (not fully hydrated)
Allow a reducing agent or compound that that converts Fe3+ into Fe2+
Such that for a given mass, the impurity would react with more dichromate
than a similar mass of FeSO4.7H20
OR for equal masses of the impurity and FeSO4.7H2O , the impurity would react with more dichromate.
Must compare mass of impurity with mass of FeSO4.7H2O
Explain why the value of Kw increases as the temperature increases. (2)
Dissociation OR breaking bonds) is endothermic M1
∴ Equilibrium moves to RHS (at higher T) to absorb heat or to lower T or oppose increase in T M2
Suggest a suitable piece of apparatus that could be used to measure out the sodium hydroxide solution.
Explain why this apparatus is more suitable than a pipette for this purpose.
Burette
Because it can deliver variable volumes
Two solutions on with a pH of 4 and one with a pH of 9 were left in the air
The pH of the pH 9.00 solution changed more than that of the other solution.
Suggest what substance might be present in the air to cause the pH to change.
Explain how and why the pH of the pH 9.00 solution changes.
M1- CO2 M2- pH (It) falls / decreases M3- acidic (gas) OR reacts with alkali(ne solution) / OH− OR CO2 + 2OH− CO32− + H2O OR CO2 + OH− HCO3−
Explain why the expression for Kw does not include the concentration of water. (3)
H2O] is very high (compared with [H+] and [OH−]) OR Very few H+ and OH− ions OR Only / very slightly dissociates OR Equilibrium lies far to the left
State what is meant by the term buffer solution.
Identify a reagent which could be added to a solution of ammonia in order to form a buffer solution (3)
Buffer solution: A solution which resists change in pH (1)
when small amounts of acid or base added or on dilution (1)
Reagent: NH4Cl (1)
State what is meant by the term Brønsted–Lowry acid.
A proton donor
Define Kw
Kw =[H+][OH-]
Define pH
-log([H+])
Hydrogen carbonate ions (HCO3−) act as a weak acid in aqueous solution. Write an equation for this equilibrium.
HCO3- _> H+ + Co3-
