A Chemistry AAQ+Level Mark
Scheme Q & A
Define the term relative atomic mass (2 marks).
.1. The average mass of an atom of an element
(average mass of all isotopes of an element)
2. Compared to 1/12th the mass of an atom of carbon-12
Describe how molecules are ionised using electrospray
ionisation (4 marks).
1. Sample dissolved (in a volatile solvent)
(allow named solvent e.g water or methanol)
2. (injected through) a needle or nozzle or capillary and at high
voltage/4000 volts or high potential
(allow needle is positively charged)
3. Gains a proton / H+
,4. X + H+ → XH+
Outline how the TOF mass spectrometer works (4 marks).
1. Positive ions are accelerated by an electric field
(allow (ions) accelerated to a negative plate)
2. To a constant kinetic energy
3. Ions create a current when hitting the detector
4. The size of the current is proportional to the abundance of
ions hitting the plate and gaining an electron
The student rinses the burette with deionised water before
filling with
sodium hydroxide solution.
State and explain the effect, if any, that this rinsing will have on
the value of
the titre (2 marks).
1. Titre value would increase / larger value
, 2. Because the sodium hydroxide solution would be more dilute
The student used a wash bottle containing deionised water
when
approaching the end-point to rinse the inside of the conical
flask.
Explain why this improved the accuracy of the titration (1
mark).
1. Idea that it ensures all ethanedioic acid / acid / sodium
hydroxide / alkali / reactants are in the mixture / solution /
reaction
OR
the idea that some of the ethanedioic acid / acid / sodium
hydroxide / alkali / reactants would be on the sides of the flask
Explain why pentan-2-ol has a higher boiling point than pent-1-
ene (3 marks).
1. Pentan-2-ol has stronger intermolecular forces
Scheme Q & A
Define the term relative atomic mass (2 marks).
.1. The average mass of an atom of an element
(average mass of all isotopes of an element)
2. Compared to 1/12th the mass of an atom of carbon-12
Describe how molecules are ionised using electrospray
ionisation (4 marks).
1. Sample dissolved (in a volatile solvent)
(allow named solvent e.g water or methanol)
2. (injected through) a needle or nozzle or capillary and at high
voltage/4000 volts or high potential
(allow needle is positively charged)
3. Gains a proton / H+
,4. X + H+ → XH+
Outline how the TOF mass spectrometer works (4 marks).
1. Positive ions are accelerated by an electric field
(allow (ions) accelerated to a negative plate)
2. To a constant kinetic energy
3. Ions create a current when hitting the detector
4. The size of the current is proportional to the abundance of
ions hitting the plate and gaining an electron
The student rinses the burette with deionised water before
filling with
sodium hydroxide solution.
State and explain the effect, if any, that this rinsing will have on
the value of
the titre (2 marks).
1. Titre value would increase / larger value
, 2. Because the sodium hydroxide solution would be more dilute
The student used a wash bottle containing deionised water
when
approaching the end-point to rinse the inside of the conical
flask.
Explain why this improved the accuracy of the titration (1
mark).
1. Idea that it ensures all ethanedioic acid / acid / sodium
hydroxide / alkali / reactants are in the mixture / solution /
reaction
OR
the idea that some of the ethanedioic acid / acid / sodium
hydroxide / alkali / reactants would be on the sides of the flask
Explain why pentan-2-ol has a higher boiling point than pent-1-
ene (3 marks).
1. Pentan-2-ol has stronger intermolecular forces
