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Chemistry > ES > Flashcards

ES Flashcards

1
Q

halogens

A

group 7 elements
7 electrons in outer shell
most reactive group of non-metals
none found naturally in elemental form

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2
Q

halogens in ionic compounds

A

gains an electron from a metal ion to form a halide ion in an ionic compound

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3
Q

colours and physical states of diatomic halogens

A

F2 - pale yellow gas at room temperature
Cl2 - green gas at room temperature
Br2 - dark red volatile liquid
I2 - shiny grey solid

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4
Q

going down the group halogens…

A

become darker in colour
MP and BP decrease
become less volatile
decrease in reactivity

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5
Q

strongest oxidising agent HALOGEN

A

decreases down group - fluorine most oxidising

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6
Q

a halogen can displace a

A

less reactive halide (eg. fluorine can displace iodide)

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7
Q

oxidation

A

gaining oxygen
loss of hydrogen
loss of electrons
ON increases

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8
Q

reduction

A

loss of oxygen
gaining hydrogen
gaining electrons
ON decreases

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9
Q

oxidising agents vs reducing agents

A

oxidising agents - oxidise others by accepting electrons, are themselves reduced

reducing agents - reduce others by donating electrons, are themselves oxidised

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10
Q

systematic names

A

include oxidation state of elements/ions with variable oxidation states eg. transition metals

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11
Q

cathode

A

negative electrode

cations (+ve) ARE REDUCED

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12
Q

anode

A

positive electrode

anions (-ve) ARE OXIDISED

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13
Q

oxidation of water

A

H2O&raquo_space; O2 + 4e- + 4H+

at anode

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14
Q

reduction of water

A

2H2O + 2e-&raquo_space; 2OH- + H2

at cathode

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15
Q

conditions for oxidation of water in electrolysis

A

O2 produced if salt is sulfate or nitrate

halogen produced if salt is halide

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16
Q

conditions for reduction of water in electrolysis

A

H2 produced if metal is group 1 or 2, aluminium, or an acide is being electrolysed
(if none of above metal is plated)

17
Q

electrolysis of hydroxides

A

4OH-&raquo_space; O2 + H2O + 2e-

at the ANODE

18
Q

dynamic equilibrium

A

concentrations of reactants and products remain constant
forward and reverse reactions both occuring
rate of forwards reaction = rate of reverse reaction

19
Q

if dynamic equilibrium is disturbed by altering the conditions

A

position of equilibrium will shift to counteract the change

20
Q

increase in availability of reactants causes equilibrium to

A

shift to right

21
Q

increase in availability of products causes equilibrium to

A

shift to left

22
Q

increasing temperature causes equilibrium to

A

shift to favour ENDOTHERMIC reaction

23
Q

increasing pressure causes equilibrium to

A

shift to side of reaction which produces fewer moles of gas

24
Q

Kc =

A

[products] / [reactants]

equilibrium constant

25
Q

Kc > 1

A

equilibrium lies to right

and if Kc > 10^10 reaction gone to completion

26
Q

uses of chlorine

A

sterilising water by killing bacteria

bleaching

27
Q

risks of chlorine

A

TOXIC gas - irritate eyes, lungs and respiratory system
can react in lungs to produce HCl
transported in tanks - if damp inside tanks HCl forms
stored in cylinders which are moved using a hoist to avoid damage
transported as liquid - more stored in smaller volume
can be transported by road/rail

28
Q

purpose of iodine-thiosulfate titrations

A

find the conc of a chemical that is a strong enough oxidising agent to oxidise iodide ions

29
Q

thermal stability of hydrogen halides

A

decreases down group (more stable at top - hydrogen fluoride)
bond strength between hydrogen and halide decreases down group 7

30
Q

acidity of hydrogen halides

A

very acidic in solution with exception of H-F

for others there is almost 100% dissociation producing oxonium ions

31
Q

reaction of hydrogen halides with ammonia

A

all react with ammonia to form salts

NH3 (g) + HCl (g)&raquo_space; NH4Cl (s)

32
Q

reactions of hydrogen halides with sulfuric acid

A

all different due to increasing strength of halides as reducing agents
HF and HCl don’t react
HBr makes SO2
HI makes H2S

33
Q

strength of reducing agents HALIDES

A

increases down group - iodide most reducing

34
Q

producing hydrogen halides from sodium halides

A

a reaction of NaF/NaCl with H2SO4 can be used to produce HF/HCl
phosphoric acid has to be used to produce HBr/HI because it won’t be reduced by bromide/iodide

Chemistry (25 decks)

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