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

What is a co-polymer?

A polymer derived from 2+ species of monomer.

Describe the structure of an A-B polymer.

Arrangement regular + alternating.

What is a benzene group otherwise known as?

A phenyl group.

Suggest the mechanism by which addition polymerisation occurs.

Electrophilic addition

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

But-1-ene + propene

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

*Ethenyl ethanoate = CH _{3}COOCH=CH_{2}*

Why does one mole of a gas always occupy 24 dm^{3 }at RTP, regardless of the size of gas molecules?

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

What is standard temperature?

273 K

0^{o}C

What volume of air is needed to completely burn 15 cm^{3} of hexane vapour? Assume that all volumes are measured at RTP and that air contains 21% oxygen.

C_{6}H_{14} + 9.5O_{2} → 6CO_{2} + 7H_{2}O

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

Vol O_{2} = 15 x 9.5 = 142.5 cm^{3}

Vol air = 142.5 x 100/21 = 680 cm^{3}

- State the ideal gas equation.
- State the units used for each quantity, excluding the constant.

**PV = nRT**

- P in Pa (Nm
^{-1}) - V in m
^{3} - n in mol
- T in K

What is the volume of 1 mole of a gas, in dm^{3}, at 100 kPa and 16^{o}C?

PV = nRT so V = nRT/P

P = 100 kPa = 100 x 10^{3} Pa

T = 16^{o}C = 289 K

V = 1 x 8.314 x 289 / (100 x 10^{3}) = 0.024 m^{3} = 24 dm^{3}

The following shows the complete combustion of octane:

C_{8}H_{18}(g) + 12.5O_{2}(g)_{ }→ 8CO_{2}(g) + 9H_{2}O(g)

3.42 g of octane is burned per second in an engine. The exhaust gases are produced at 550^{o}C and 1.50 x 10^{5} Pa.

Calculate the volume of exhaust gases, in dm^{3}, produced per second. Assume that carbon dioxide and water vapour are the only gases present in the exhaust.

**Rearrange equation**

pV = nRT → V = nRT/P

**Find n, combined mol of CO _{2} + H_{2}O**

n octane = 3.42/114 = 0.03

Therefore n (CO_{2} + H_{2}O) = 0.03 x (8 + 9) = 0.51 mol

**Convert temperature**

550^{o}C + 273 = 823 K

**Find volume in m ^{3} and convert to dm^{3}**

V = (0.51 x 8.314 x 823) / (1.5 x 10^{5}) = 0.0233 m^{3}

x 10^{3} = 23.3 dm^{3}

Hydrogen can be stored in car tanks at a pressure of 7.0 × 10^{4} kPa.

The volume of a tank is 70 dm^{3} and the temperature 20°C. Calculate the maximum energy that could be produced by burning all the hydrogen in the tank.

∆_{c}H for H_{2} = –242 kJ mol^{-1}

Give your answer in standard form, to two significant figures.

pV = nRT → n = PV/RT

P = 7 x 10^{4} kPa = 7 x 10^{7} Pa

V = 70 dm^{3} = 70 x 10^{-}^{3} m^{3}

T = 20^{o}C = 293 K

Mol H_{2} = n = (7 x 10^{7} x 70 x 10^{-3}) / (8.314 x 293) = 2011 mol

E = 2011 x 242 = 490,000 kJ = 4.9 x 10^{5} kJ

What are structual isomers?

- Same molecular formulae
- Different structural formulae (ordering of atoms)

Name and describe the 3 types of structural isomerism.

**Chain:** different branching of chains; 4+ carbons needed

**Position:** different locations of a functional group

**Functional group:** different functional groups / homologous series