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Chemistry > A1- Relating Properties to Uses & Production of Substances > Flashcards

A1- Relating Properties to Uses & Production of Substances Flashcards

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1
Q

Describe the electrolysis of brine

Electrolysis of Brine

A

There are 4 ions present in cell; Na+, Cl-, H+ & OH-
It’s carried out in aq solution
Chloride ions lose e- to form molecules
Hydrogen ions gain e- to form molecules
3 major PRODUCTS from process = H2 (g), Cl2 (g), NaOH (aq)

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2
Q

H2 uses…
Cl2 uses…
NaOH uses…

Electrolysis of Brine

A

H2 = rocket fuel/ to make ammonia & fertilisers
Cl2 = bleach
NaOH = plastics, soaps, oven cleaner

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3
Q

Why is a membrane cell used?

Electrolysis of Brine

A
  • allows Na+ ions to pass thru membrane but Cl- ions cannot
  • prevents contamination of NaOH w/ NaCL
  • separates chlorine & hydrogen
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4
Q

Why is the level of brine higher than NaCl side?

Electrolysis of Brine

A

To prevent NaOH flowing back and mixing w/ chlorine - ensures flow of liquid is always left to right

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5
Q

Briefly explain the Hall-Heroult process

Hall Heroult

A

O2- ions move to positive electrode + O2 produces at anode - then reacts w/ carbon in anode to produce CO2

Al3+ ions move to negative electrode & molten aluminium is then produced at cathode

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6
Q

Why is aluminium oxide dissolved in MOLTEN cryolite?

Hall Heroult

A

As a solvent it reduces energy costs to actually extract by allowing ions in Al2O3 to move freely at lower temp (so they can carry a current)

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7
Q

What are the equations at each electrode?

Hall Heroult

A

Al3+ + 3e- = Al reduction, gain e-

2O2- = O2 + 4e- oxidation, lose e-

C + O2 = CO2

= ARROW

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8
Q

Give 2 reasons why electrolysis of alumina is expensive

Hall Heroult

A

Alumina requires a lot of energy to melt due to high melting point
Graphite anodes need to be replaced regularly
Requires a lot of electricity

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9
Q

State the equations for electrolysis of brine

A

Hydrogen produced at Cathode:
2H+ + 2e- = H2

Chlorine produced at Anode:
2Cl- + 2e- = Cl2

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10
Q

Describe where each product is FORMED during electrolysis of Brine

A
  • hydrogen produced at Cathode
  • chlorine produced at Anode
  • sodium hydroxide is left over solution
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11
Q

Explain why carbon positive electrodes need to be replaced regularly

Hall Heroult

A

Oxygen builds up regularly at positive electrode
- Carbon electrodes react w/ O2
- O2 produced at electrode

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12
Q

The basis of Electrolysis:

A

Must conduct electricity so MOLTEN ionic compound used so ions can move + carry charge/current

Cations move towards cathode & anions move towards anode - flow of electric charge

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13
Q

Describe how electrolysis of sodium chloride produces chlorine

Electrolysis of Sodium Chloride

A
  • Melt or Dissolve NaCl
  • pass current thru NaCl
    ~ Cl moves to anode
    ~ Cl- loses e- to form Cl2
  • 2Cl- = Cl2 + 2e-
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14
Q

Example of acids

A
  • nitric acid ~ HNO3
  • hydrochloric acid ~ HCl
  • sulfuric acid - H2SO4
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15
Q

What is a salt & provide examples?

A

Salt formed when H+ in acid have been REPLACED by diff positive ions

Nitrate salts ~ NO3-
Chloride salts ~ Cl-
Sulfate salts ~ SO4 2-

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16
Q
  • Metal hydroxides are…
  • What is an alkali
A
  • alkalis
  • a base that dissolves in water, OH- ions are formed
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17
Q
  • metal oxides are….
  • what is a base?
A
  • bases
  • bases react w/ acids to form salt & water
    Metal oxide + acid = salt + water
    CaO + 2HCl = CaCl2 + H2O
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18
Q
  • use of magnesium hydroxide?
  • calcium hydroxide uses?
  • aluminium oxide uses?
  • sodium hydroxide uses?
A
  • treating stomach acid indigestion ~ raises pH of stomach acid
  • treating acidic effluent (waste) ~ raises pH of acidic soil by farmers - H2SO4 + Ca(OH)2 = CaSO4 + 2H2O
  • paint & sunscreen, lining furnaces ~ INHERT & high melting point
  • makes plastics & soaps, drain cleaner & oven cleaner
19
Q

What is the general formula for group 2 hydroxides?

A

X(OH)2

20
Q
  • Properties of SO2, Al2O3, MgO?
  • what does amphoteric mean?
A
  • SO2 ~ acid, Al2O3 ~ amphoteric, MgO ~ base
  • acts as both an acid & base
21
Q

Non metal oxides are acidic & metal oxides are bases
True or false?

A

True :)

22
Q

Define transition metals

A

Metals that form an ion w/ a partially filled d-subshell

23
Q

What are TMs good at?

TMs = transition metals

A

Good at speeding up reactions ~ good CATALYSTS

24
Q

Explain how a catalysts lowers amount of energy needed for reactions

A
  • Catalysts ADSORBS reactants on it’s surface by weakening bonds
  • because e- are accepted & donated back ~ providing alternative route for reaction w/ lower activation energy
  • so, collisions w/ lower energy will react
25
Q

Define a catalyst

A

Speeds up reactions by providing an alternative pathway

26
Q

Explain why TM act as catalysts

A
  • have partially filled d-subshell
  • accept/lose e- ~ meaning they can be oxidised or reduced - providing an alternative route for reaction w/ lower activation energy
27
Q

State balanced equation got reactions between calcium hydroxide & hydrochloric acid

A

Ca (OH)2 + 2HCl - CaCl2 + 2H2O

28
Q

picture of complex ion of 6 water molecules boned to a central vanadium (lll) ion

Describe how water molecules are bonded to vanadium (lll) ion

A

Pair of e- shared between H2O and the vanadium ~ coordinate bond formed

29
Q

Why is Ti used in hip replacement surgery?

A

Low reactivity & low density

30
Q

State equation for Stage 1 of Kroll process

A

TiO2 + 2Cl2 + 2C = TiCl4 + CO2

31
Q

Equation for Stage 2 of Kroll process

A

Magnesium:
TiCl4 + 2Mg = Ti + 2MgCl2

Sodium:
TiCl4 + 4Na = 4NaCl + Ti

32
Q

In stage 1 titanium is converted into…

A

TiCl4

33
Q

In stage 2 titanium is reduced by…

A

Magnesium & sodium

34
Q

What is the ore of titanium called?

A

Rutile

35
Q

What is the formula of titanium (IV)?

A

TiO2

36
Q

Which gas prevents reaction w/ O2 or nitrogen

A

Argon ~ prevents titanium becoming brittle & oxidation of Ti

37
Q

What is titanium IV oxide heated up w/?

A

Chlorine gas & coke

38
Q

Why is Ti used in aircraft?

A

It has Low Density

39
Q

Name the Bayer process

A
  • bauxite ore crushed to form grains ~ this speeds up rate of reaction
  • reacted w/ conc. hot sodium hydroxide under pressure ~ bc alumina is amphoteric so can react w/ alkali NaOH
  • forms a slurry
  • alumina dissolved, impurities DO NOT ~ alumina is amphoteric & impurities are basic so they do NOT dissolve
  • IMPURITIES filtered off
  • solution cooled & aluminium hydroxide added to cause crystallisation
  • aluminium hydroxide filtered off & then heated in a kiln to form alumina!
40
Q

What is sodium hydroxide?

A

An alkali

41
Q

Why does alumina react w/ sodium hydroxide?

A

Alumina reacts w/ it because it’s amphoteric

42
Q

Write the balanced equation for bayer process

A

2Al (OH)3 —> Al2O3 + 3H2O

43
Q

name two correctly balanced equations forming alkalis

A

CaO + H2O —> Ca(OH)2

Na2O + H2O —> 2NaOH

44
Q

Definition of Electrolysis

A

Chemistry (3 decks)

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