Halogenoalkanes

Question 1

General formula of halogenoalkanes

Answer 1

CnH2n-1 X

Question 2

Uses of halogenoalkanes

Answer 2

Regrigerators
Aerosal propellants
Degreasing agents
Dry cleaning solvents

Question 3

Reactivity of haogenoalkanes

Answer 3

Polar carbon bonds
C-F is the most electronegative
Halogens are > electronegative than carbon
Bonded electron attracted more to halogen

Question 4

Trend in electronegativity of halogens and effect

Answer 4

decreases down the group and reduces polarity

Question 5

What are nucleophiles attractd to

Answer 5

Electron deficient carbon atoms

Question 6

What is hydrrolysis

Answer 6

reaction with water of aqueous sodium hydroxide that breaks a chemical compound

Question 7

process of hydrolysis

Answer 7

Halogen atom replaced by Hydroxide ion
OH- ion has a lone pair of electrons- attracted and donated to the electron deficient carbon atom- NUCLEOPHILLIC ATTACK

Donation of electronpair leads to formation of a new covalent bond

Carbon halogen bond breaks by HETEROLYTIC FISSION - both electrons move to halogen- halide ion

Question 8

Reagents needed for measuring the rate of hydrolysis

Answer 8

Silver nitrate-
ethanol- common solvent mixes silver nitrate mixes
water- nucleophile

Question 9

Procedure to measure rate of hydrolysis of halogenoalkane

Answer 9

measure each halogenoalkane into a separate tube
place in water bath at 50 degrees
Put a solution fo ethanol, water and AGNO3 into another testube

once all test tubes have reaches same temp, add equal volumes of each mixture to each halogenoakane

time how long it takes for a precipitate to form

Question 10

Bond polarity vs enthalpy

Answer 10

Polarity suggest that C-F is the most electronegative and most likely to attract a nuclophile- so fastest rate

Enthalpy suggests that C-I bond is weakest, easiest to break and faster reaction

Enthalpy is mire significant

Question 11

Nucleophillic substitution

Answer 11

Type of sub reaction
Nuclophile attracted to electron deficient centre
donates a pair of electrons
forms a new covalent bond

Question 12

How does the C-F bond affect PTFE

Answer 12

Its very strong
making the polymer INERT
RESISTANT TO CHEMICAL ATTACK
HEAT RESISTANT 
perfect for coating pans

Question 13

What’s the problem with CFC’s

Answer 13

They are broken down in the stratosphere
UV breaks them down into radicals
These catalyse the break down of the ozone layer
depletion of ozone has allowed harmful UV to reach lower atmospher> skin cancer

Question 14

alternatives to CFC’s

Answer 14

Hydroflurocarbons non flammable non toxic

Question 15

What were CFC@s initially used for

Answer 15

aersols propellants regiragents solvents

Question 16

Problem with HCFC

Answer 16

still cause ozone depletion

depleting effect is a lot less than CFC’s

Question 17

uses of PVC

Answer 17

drainpipes
plastic window frames
sports equipment

Question 18

Perecentage yield

Answer 18

actual amount in mole over theoretical amount in mole

Question 19

Atom economy

Answer 19

moleclar mass of useful product over molecular mass of all products