# DF aprst: Polymers; ideal gas equation; isomerism Flashcards

1
Q

What is a co-polymer?

A

A polymer derived from 2+ species of monomer.

2
Q

Describe the structure of an A-B polymer.

A

Arrangement regular + alternating.

3
Q

What is a benzene group otherwise known as?

A

A phenyl group.

4
Q

Suggest the mechanism by which addition polymerisation occurs.

A

Double bond attacks an electrophile, forming a carbocation which further double bonds attack in a domino-like manner

5
Q
A

But-1-ene + propene

6
Q

Draw the repeating unit of the A-B copolymer formed when chloroethene and ethenyl ethanoate undergo addition polymerisation.

A

Ethenyl ethanoate = CH3COOCH=CH2

7
Q

Why does one mole of a gas always occupy 24 dm3 at RTP, regardless of the size of gas molecules?

A

Variations in molecular size are negligable compared to the distance between molecules.

8
Q

What is standard temperature?

A

273 K

0oC

9
Q

What volume of air is needed to completely burn 15 cm3 of hexane vapour? Assume that all volumes are measured at RTP and that air contains 21% oxygen.

A

C6H14 + 9.5O2 → 6CO2 + 7H2O

Equal moles of any two gases occupy the same volume at RTP

Vol O2 = 15 x 9.5 = 142.5 cm3

Vol air = 142.5 x 100/21 = 680 cm3

10
Q
• State the ideal gas equation.
• State the units used for each quantity, excluding the constant.
A

PV = nRT

• P in Pa (Nm-1)
• V in m3
• n in mol
• T in K
11
Q

What is the volume of 1 mole of a gas, in dm3, at 100 kPa and 16oC?

A

PV = nRT so V = nRT/P

P = 100 kPa = 100 x 103 Pa

T = 16oC = 289 K

V = 1 x 8.314 x 289 / (100 x 103) = 0.024 m3 = 24 dm3

12
Q

The following shows the complete combustion of octane:

C8H18(g) + 12.5O2(g) → 8CO2(g) + 9H2O(g)

3.42 g of octane is burned per second in an engine. The exhaust gases are produced at 550oC and 1.50 x 105 Pa.

Calculate the volume of exhaust gases, in dm3, produced per second. Assume that carbon dioxide and water vapour are the only gases present in the exhaust.

A

Rearrange equation

pV = nRT → V = nRT/P

Find n, combined mol of CO2 + H2O

n octane = 3.42/114 = 0.03

Therefore n (CO2 + H2O) = 0.03 x (8 + 9) = 0.51 mol

Convert temperature

550oC + 273 = 823 K

Find volume in m3 and convert to dm3

V = (0.51 x 8.314 x 823) / (1.5 x 105) = 0.0233 m3

x 103 = 23.3 dm3

13
Q

Hydrogen can be stored in car tanks at a pressure of 7.0 × 104 kPa.

The volume of a tank is 70 dm3 and the temperature 20°C. Calculate the maximum energy that could be produced by burning all the hydrogen in the tank.

cH for H2 = –242 kJ mol-1

A

pV = nRT → n = PV/RT

P = 7 x 104 kPa = 7 x 107 Pa

V = 70 dm3 = 70 x 10-3 m3

T = 20oC = 293 K

Mol H2 = n = (7 x 107 x 70 x 10-3) / (8.314 x 293) = 2011 mol

E = 2011 x 242 = 490,000 kJ = 4.9 x 105 kJ

14
Q

What are structual isomers?

A
• Same molecular formulae
• Different structural formulae (ordering of atoms)
15
Q

Name and describe the 3 types of structural isomerism.

A

Chain: different branching of chains; 4+ carbons needed

Position: different locations of a functional group

Functional group: different functional groups / homologous series

16
Q

What are stereo isomers?

A
• Same molecular formulae
• Same structural formulae (ordering of atoms)
• Different spatial arrangement of atoms
17
Q

Name and define the 2 types of stereoisomerism. State any requirements for each type to arise.

A

E/Z or cis/trans or geometric: Lack of free rotation about C=C bonds with different groups on each carbon:

• Z/cis: same groups on upper or lower side of double bond (“zame side”)
• E/trans: same groups on opposite upper/lower sides of double bond

Optical: Isomers are mirror images of each other; must be non-symmetrical

18
Q
• Name these molecules
• Which type of isomerism is shown here?
A
• Butane + methylpropane
• Chain structural isomerism
19
Q
• Name these molecules
• Which type of isomerism is shown here?
A
• Propan-1-ol + propan-2-ol
• Position structural isomerism
20
Q
• Name these molecules and state the homologous series to which they belong
• Which type of isomerism is shown here?
A
• Propan-1-ol (alcohol, -OH) + methoxyethane (ether, -O-)
• Functional group structural isomerism
21
Q
• Name these molecules
• Which type of isomerism is shown here?
A
• E(trans)-but-2-ene, Z(cis)-but-2-ene
• E/Z or cis/trans or geometrical stereo isomerism
22
Q
A

a) E/Z isomers
b) 2 mol
c) Citranellol has 1 fewer double bonds / is partially hydrogenated
d) Position structural isomers