challenging areas

Question 1

saturated solution

Answer 1

A solution in which the maximum amount of solute is dissolved, at that temperature

Question 2

unsaturated solution

Answer 2

A solution in which less than the maximum amount of solute is dissolved, at that temperature

Question 3

Supersaturated Solution

Answer 3

A solution in which more than the maximum amount of solute is dissolved, at that temperature. This is an unstable situation which can arise when a saturated solution cools, and is likely to result in crystallisation of some of the solute

Question 4

Crystallisation

Answer 4

Where a dissolved solute forms a solid due to it being in a supersaturated solution. This often arises due to the cooling of a saturated solution; the slower the solution cools the larger the crystals appear.

Question 5

Polyprotic Acids

Answer 5

Species that donates multiple protons, H+, during ionisation

Question 6

Amphiprotic Species

Answer 6

Amphiprotic species can either donate or accept a proton, H+.

Question 7

Monoprotic

Answer 7

Species that donates one proton, H+, during ionisation
Example: HCl, HNO3 or NH4+

Question 8

Diprotic

Answer 8

Species that donates two protons, H+, during ionisation
Example: H2SO4 or H2CO3

Question 9

Triprotic

Answer 9

Species that donates three protons, H+, during ionisation
Example: H3PO4

Question 10

Acidic Oxides

Answer 10

Acidic oxides reacting with water producing acids.
When an acidic oxide is dissolved in water, it will decrease the pH of the water sample due to the formation of H+ions. Some common examples for acidic oxides are CO2, NO2 and SO2.

Question 11

Oxidation number rules

Answer 11

1. Sum = overall charge.
2. Fluorine is -1 in compounds.
3. Group 1 and 2 metals are +1 and +2 respectively (in compounds)
4. H bonded to non-metals is +1, bonded to metals is -1.
5. O is -2 in compounds, except for peroxides where it is -1.
6. Group 7 are usually -1 in compounds. If >1 halogen is present, the most electronegative is -1.
7. Where no other priority exists, Group 6 NMs are usually -2, Group 15 NMs usually -3 and Group 3 metals usually +3.

Question 12

Sacrificial Anode

Answer 12

A more reactive metal in contact with iron, that oxidises preferentially instead of the iron.

Question 13

Storage cell

Answer 13

A galvanic cell in which the reactant chemicals are not replenished and will eventually run out.

Question 14

How do you identify the base peak in Mass Spectrometry?

Answer 14

The highest peak (most abundant fragment)

Question 15

How do you identify the parent or molecular ion (M) peak in Mass Spectrometry? What information does it give us?

Answer 15

The furthest peak to the right (excluding very small peaks). This shows the molar mass of the parent molecule.

Question 16

How to determine the number of C atoms in a particular environment from an NMR spectrum

Answer 16

Relative peak height or peak area (often called an integral)

Question 17

Which wavenumber range is most useful for identifying bonds using IR?

Answer 17

Above wavenumbers of 1500cm^-1

Question 18

How to determine number of C environments from an NMR spectrum

Answer 18

Number of peaks (ignoring any ‘peak splitting’)

Question 19

In chromatography, what is the difference between an Rf value and an Rt value?

Answer 19

An Rf value (the retention factor) in paper chromatography or TLC is the distance travelled by a component relative to the solvent front, whereas an Rt value (the retention time) in column chromatography is the time taken for a component to pass through the column.