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Chem Unit 2 6/13,1/13,6/12, 1/12, 6/11, 1/11, 6/10, 1/10, 6/09 > Halogens more > Flashcards

Halogens more Flashcards

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1
Q

Fluorine

A

very pale yellow gas. Highly reactive.

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2
Q

Chlorine

A

greenish, reactive gas, poisonous in high concentration

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3
Q

Bromine

A

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

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4
Q

Iodine

A

shiny grey solid sublimes to purple gas

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5
Q

trend in melting point and boiling point

A

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

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6
Q

trends in electronegativity

A

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

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7
Q

Oxidising strength trend in halogens

A

decreases down the group

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8
Q

what are oxidising agents

A

Oxidising agents are electron acceptors

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9
Q

Chlorine with potassium chloride

A

Very pale green, no reaction

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10
Q

Chlorine with potassium bromide

A

yellow solution, Cl has displaced Br

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11
Q

Chlorine with potassium iodide

A

Brown solution, Cl has displaced I

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12
Q

Bromine with potassium chloride

A

Yellow so no reaction

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13
Q

Bromine with potassium bromide

A

Yellow solution, no reaction

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14
Q

Bromine with potassium iodide

A

Brown solution, Br has displaced I

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15
Q

What does the colour in the solution suggest

A

Shows which free halogen is present in solution.

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16
Q

Fluoride with silver nitrate

A

no precipitate

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17
Q

Chlorides with silver nitrate

A

white precipitate

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18
Q

Bromide with silver nitrate

A

cream precipitate

19
Q

Iodide with silver nitrate

A

yellow precipitate

20
Q

why is ammonia used ?

A

to differentiate between the halides if the colours look similiar

21
Q

does silver chloride dissolves in dilute ammonia

A

yes

22
Q

does silver bromide dissolve in dilute ammonia

A

no, but yes in concentrated ammonia

23
Q

Does silver iodide dissolve in ammonia

A

no, not even in concentrated ammonia

24
Q

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

A

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

25
Q

Reaction of halide salts with concentrated sulphuric acid: With Bromide

A

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

26
Q

Reaction of halide salts with concentrated sulphuric acid : With Iodide

A

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

27
Q

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

A

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

28
Q

DISPROPORTIONATION

A

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

29
Q

Chlorine with cold water

A

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

30
Q

Chlorine with water in sunlight

A

2Cl2 + 2H2O –> 4H+ + 4CL + O2

31
Q

Reactio of chlorine with cold dilute NaOH

A

Cl2 + 2NaCl –> NaCl +NaOCl + H2O

32
Q

Uses of chlorine

A

kills bacteria in pools and used as bleach

33
Q

why can we use chlorine in pools

A

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

34
Q

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).

A

CH4 + 3F2—————> CHF3 + 3HF

35
Q

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

A

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

36
Q

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

A

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

37
Q

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

A

I-Cl- or Br-Ag+ + I− ——->AgI

38
Q

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.

A

H2SO4 + NaCl——->NaHSO4 + HClAcid

39
Q

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

A

(+) 6; (+) 4;

40
Q

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 .

A

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

41
Q

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

A

Hydrogen sulphide; Bad egg smell; Sulphur;Yellow solid

42
Q

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

A

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

43
Q

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

A

Greater surface area making more collisons possible

44
Q

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

A

No effectRate of forward and backward reaction increased equally

Chem Unit 2 6/13,1/13,6/12, 1/12, 6/11, 1/11, 6/10, 1/10, 6/09 (10 decks)

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