Halogens more

Question 1

Fluorine

Answer 1

very pale yellow gas. Highly reactive.

Question 2

Chlorine

Answer 2

greenish, reactive gas, poisonous in high concentration

Question 3

Bromine

Answer 3

red liquid, that gives off dense brown/orange poisonous fumes

Question 4

Iodine

Answer 4

shiny grey solid sublimes to purple gas

Question 5

trend in melting point and boiling point

Answer 5

Increase down the group, molecules become larger and have more electrons and so have larger van der waal forces.

Question 6

trends in electronegativity

Answer 6

decreases- the atomic radius increases due to the increasing number of shells. Nucleus less able to attract

Question 7

Oxidising strength trend in halogens

Answer 7

decreases down the group

Question 8

what are oxidising agents

Answer 8

Oxidising agents are electron acceptors

Question 9

Chlorine with potassium chloride

Answer 9

Very pale green, no reaction

Question 10

Chlorine with potassium bromide

Answer 10

yellow solution, Cl has displaced Br

Question 11

Chlorine with potassium iodide

Answer 11

Brown solution, Cl has displaced I

Question 12

Bromine with potassium chloride

Answer 12

Yellow so no reaction

Question 13

Bromine with potassium bromide

Answer 13

Yellow solution, no reaction

Question 14

Bromine with potassium iodide

Answer 14

Brown solution, Br has displaced I

Question 15

What does the colour in the solution suggest

Answer 15

Shows which free halogen is present in solution.

Question 16

Fluoride with silver nitrate

Answer 16

no precipitate

Question 17

Chlorides with silver nitrate

Answer 17

white precipitate

Question 18

Bromide with silver nitrate

Answer 18

cream precipitate

Question 19

Iodide with silver nitrate

Answer 19

yellow precipitate

Question 20

why is ammonia used ?

Answer 20

to differentiate between the halides if the colours look similiar

Question 21

does silver chloride dissolves in dilute ammonia

Answer 21

yes

Question 22

does silver bromide dissolve in dilute ammonia

Answer 22

no, but yes in concentrated ammonia

Question 23

Does silver iodide dissolve in ammonia

Answer 23

no, not even in concentrated ammonia

Question 24

Reaction of halide salts with concentrated sulphuric acid: fluoride and chloride

Answer 24

Not strong enough reducing agents to reduce the S in H2SO4- ONLY ACID BASE reactions occurNaF + H2SO4 –> NaHSO4 + HbrWHITE STEAMY FUMES OF HCL ARE INVOLVED

Question 25

Reaction of halide salts with concentrated sulphuric acid: With Bromide

Answer 25

two steps: acid base step (initially reduces sulfur) and redox step Acid base step: NaBr + H2SO4 --> NaHSO4 + HFRedox step: 2HBr +H2SO4 --> Br2 + SO2 + 2H2O.White steamy fumes of HBr are evolved. Red fumes of Bromine are also involved and a colourless, acidic gas SO2H2SO4 acts as acid in first step to produce HBr and is an oxidising agent

Question 26

Reaction of halide salts with concentrated sulphuric acid : With Iodide

Answer 26

Strongest reducing agent- reduce sulfure from +6 to +4 in SO2 and from 0 to -2 in H2SWhite steamy fumes of HI involved. Black solid and purple fumes of idone are also involved. Colourless, acidic gas SO2, yellow solid of sulfur, H2S a gas with a bad egg smell

Question 27

Reaction of halide salts with concentrated sulphuric acid: 4 steps of Iodide

Answer 27

NAI + H2SO4 --> NaHSO4 + HI2HI + H2SO4 --> I2 + SO2 +2H2O2HI + H2SO4 --> 3I2 + S + 4H2O8HI + H2SO4 --> 4I2 + H2S + 4H20

Question 28

DISPROPORTIONATION

Answer 28

The name for a reaction where an element simultaneously oxidises and reduces

Question 29

Chlorine with cold water

Answer 29

Cl2 + H2O --> HOCL +HCL- Chlorine is simultaneously reducing and oxidising

Question 30

Chlorine with water in sunlight

Answer 30

2Cl2 + 2H2O --> 4H+ + 4CL + O2

Question 31

Reactio of chlorine with cold dilute NaOH

Answer 31

Cl2 + 2NaCl --> NaCl +NaOCl + H2O

Question 32

Uses of chlorine

Answer 32

kills bacteria in pools and used as bleach

Question 33

why can we use chlorine in pools

Answer 33

Used in sufficiently small amounts and the benefits to health of water treatment outweigh its toxic effect

Question 34

Halogens are used to make halogenated organic compounds.The refrigerant used in air conditioners is a mixture of fluorinated alkanes.These compounds are made by fluorination reactions.The mechanism for the reaction of fluorine with an alkane or with a fluoroalkane is a free-radical substitution similar to the reaction of chlorine with methane.Write the overall equation for the reaction of fluorine with methane to form trifluoromethane (CHF3).

Answer 34

CH4 + 3F2---------------> CHF3 + 3HF

Question 35

Write equations for the following steps in the mechanism for the reaction of fluorine with trifluoromethane (CHF3) to form tetrafluoromethane (CF4).Initiation step............................................................................................................................................ First propagation step............................................................................................................................................ Second propagation step............................................................................................................................................ A termination step leading to the formation of hexafluoroethane

Answer 35

InitiationF2 ---->2F•First propagationF• + CF3 ----> •CF3 +HFSecond propagationF2 + •CF3 ---->CF4 + F•Termination (must make C2F6)2 •CF3 ----> C2F6 or CF3CF3

Question 36

Identify a bond in a CFC that is broken by ultra-violet radiation to produce a reactive intermediate.Give the name of this reactive intermediate that catalyses the decomposition of ozone. Write an overall equation for this decomposition of ozone.Bond broken ....................................................................................................................... Name of the reactive intermediate .................................................................................….Overall equation

Answer 36

*C―Cl bond OR carbon-chlorine bond *chlorine atom OR chlorine (free) radical* 2O3 ----> 3O2

Question 37

When silver nitrate solution is added to a mixture containing two different halide ions in solution, two different precipitates, R and S, are formed. When concentrated ammonia solution is then added, R remains as a precipitate and S dissolves completely.Identify the halide ion in RIdentify a possible halide ion in SWrite an ionic equation for the formation of the precipitate R from silver nitrate

Answer 37

I-Cl- or Br-Ag+ + I− ------->AgI

Question 38

When concentrated sulphuric acid is added to solid sodium chloride a reaction occurs in which misty fumes are formed.Write an equation for this reactionState the role of sulphuric acid in this reaction.

Answer 38

H2SO4 + NaCl------->NaHSO4 + HClAcid

Question 39

When concentrated sulphuric acid is added to solid sodium bromide, a redox reaction occurs. A mixture of gases, including sulphur dioxide, is formed.State the oxidation state of sulphur in sulphuric acid and in sulphur dioxide.Oxidation state of sulphur in sulphuric acid ...........................................................Oxidation state of sulphur in sulphur dioxide

Answer 39

(+) 6; (+) 4;

Question 40

Write an equation for the redox reaction between concentrated sulphuric acid and solid sodium bromide. State the role of sulphuric acid in this reaction.Equation Role of sulphuric acid .

Answer 40

H2SO4+2H+ +2Br− --------> Br2 +SO2 +2H2O; Oxidising agent / electron acceptor;

Question 41

When concentrated sulphuric acid is added to solid sodium iodide a redox reaction occurs to produce sulphur dioxide. Two other reduction products are formed.Identify these two other reduction products. In each case, state an observation that would confirm the identity of the product.Reduction product 1 ObservationReduction product 2 Observation

Answer 41

Hydrogen sulphide; Bad egg smell; Sulphur;Yellow solid

Question 42

State and explain the effect on the rate of a reaction involving gases when the volume of the container is decreased but the number of gas particles and the temperature stay the same (3)Effect Explanation

Answer 42

IncreasesMore collisions; Particles closer together / greater concentration / increased pressure;

Question 43

Give one reason why a metal catalyst is often used in the form of a gauze or a powder.

Answer 43

Greater surface area making more collisons possible

Question 44

State and explain the effect on the equilibrium yield of a reaction when a catalyst is used.Effect on equilibrium yield Explanation

Answer 44

No effectRate of forward and backward reaction increased equally