Notes From Past Papers

Question 1

What is the temperature at which the entropy of a perfect crystal is zero

Answer 1

0k

Question 2

What is le chateliers principle

Answer 2

If a system is subjected to any change the system will readjust itself to counteract the applied change

Question 3

Why use a pH meter instead of an indicator

Answer 3

If the colour change is too hard to see

Question 4

Why use reflux

Answer 4

Prevent evaporation of volatile molecules

Question 5

If titre values are small (<10) what can you do?

Answer 5

• tire ate a larger sample

* dilute the standard

Question 6

Why use volumetric instead of gravemetric

Answer 6

If gravemetric would produce too little or no precipitate

Question 7

Why would the optical activity of a solution decrease

Answer 7

When a racemic mixture has been formed

Question 8

What is a covalent bond

Answer 8

One atom in the molecule provides both of the bond in electrons

Question 9

Why doesn’t a primary haloalkane do Sn1

Answer 9

The carbonation is not stable enough to exists

Question 10

What is an agonist

Answer 10

Mimics the natural response of the body

Question 11

What is an antagonist

Answer 11

Prevents the natural response of the body

Question 12

What is the pharmacophore

Answer 12

Area responsible for the desired effect

Question 13

What is a receptor

Answer 13

Site where reaction occurs

Question 14

Why do tertiary/secondary haloalkanes undergo Sn1

Answer 14

Have more than 1 alkyl group, which stabilises the molecules allowing the carbocation to be able to exist

Question 15

Neon produced a red light because?

Answer 15

When electron falls down from promoted energy level, it emotes radiation from the red end of the spectrum

Question 16

Describe the emission spectrum

Answer 16

• energy absorbed results in electrons being promoted to higher energy levels
• when it falls back down, energy is emitted in the form of a photon whose wavelength corresponds to (colour) light

Question 17

How is colorimeter my performed

Answer 17

• the absorbable of several solution of accurately known concentrations are measured
• a calibration graph is plotted with data
• absorbable of unknown is measured and compared against graph to deduce concentration

Question 18

Why is NaOH an unsuitable standard

Answer 18

Low GFM
unstable is air (CO2)
absorbs moisture in air

Question 19

In solvent extraction:

Why Gould you replace the aqueous layer with a different solvent instead of water

Answer 19

Less solute dissolves in that solvent

Question 20

Why doesn’t benzene conduct electricity

Answer 20

The delocalised electrons are restricted to the ring

Question 21

What is TMS

Answer 21

The standard referencing substance

Question 22

What is a back titration

Answer 22

When the substance isn’t got rated itself but reacted with an excess solution

•then the remaining solution is reacted with something else to see how much was left over

Question 23

What is homolytic fission and where does it occur

Answer 23

When the bond breaks and each atom in the bond receives an electron each forming free radicals

Usually occurs in non-polar covalent bonds

Question 24

What is heterolyic bond fission and where does it occur

Answer 24

When one atom in the bond receives both the bonding electrons. This forms ions

Occurs between polar covalent bonds