A1- Relating Properties to Uses & Production of Substances

Question 1

Describe the electrolysis of brine

Electrolysis of Brine

Answer 1

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)

Question 2

H2 uses…
Cl2 uses…
NaOH uses…

Electrolysis of Brine

Answer 2

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

Question 3

Why is a membrane cell used?

Electrolysis of Brine

Answer 3

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

Question 4

Why is the level of brine higher than NaCl side?

Electrolysis of Brine

Answer 4

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

Question 5

Briefly explain the Hall-Heroult process

Hall Heroult

Answer 5

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

Question 6

Why is aluminium oxide dissolved in MOLTEN cryolite?

Hall Heroult

Answer 6

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)

Question 7

What are the equations at each electrode?

Hall Heroult

Answer 7

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

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

C + O2 = CO2

= ARROW

Question 8

Give 2 reasons why electrolysis of alumina is expensive

Hall Heroult

Answer 8

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

Question 9

State the equations for electrolysis of brine

Answer 9

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

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

Question 10

Describe where each product is FORMED during electrolysis of Brine

Answer 10

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

Question 11

Explain why carbon positive electrodes need to be replaced regularly

Hall Heroult

Answer 11

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

Question 12

The basis of Electrolysis:

Answer 12

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

Question 13

Describe how electrolysis of sodium chloride produces chlorine

Electrolysis of Sodium Chloride

Answer 13

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

Question 14

Example of acids

Answer 14

• nitric acid ~ HNO3
• hydrochloric acid ~ HCl
• sulfuric acid - H2SO4

Question 15

What is a salt & provide examples?

Answer 15

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

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

Question 16

• Metal hydroxides are…
• What is an alkali

Answer 16

• alkalis
• a base that dissolves in water, OH- ions are formed

Question 17

• metal oxides are….
• what is a base?

Answer 17

• bases
• bases react w/ acids to form salt & water
  Metal oxide + acid = salt + water
  CaO + 2HCl = CaCl2 + H2O

Question 18

• use of magnesium hydroxide?
• calcium hydroxide uses?
• aluminium oxide uses?
• sodium hydroxide uses?

Answer 18

• 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

Question 19

What is the general formula for group 2 hydroxides?

Answer 19

X(OH)2

Question 20

• Properties of SO2, Al2O3, MgO?
• what does amphoteric mean?

Answer 20

• SO2 ~ acid, Al2O3 ~ amphoteric, MgO ~ base
• acts as both an acid & base

Question 21

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

Answer 21

True :)

Question 22

Define transition metals

Answer 22

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

Question 23

What are TMs good at?

TMs = transition metals

Answer 23

Good at speeding up reactions ~ good CATALYSTS

Question 24

Explain how a catalysts lowers amount of energy needed for reactions

Answer 24

• 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

Question 25

Define a catalyst

Answer 25

Speeds up reactions by providing an alternative pathway

Question 26

Explain why TM act as catalysts

Answer 26

- 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

Question 27

State balanced equation got reactions between calcium hydroxide & hydrochloric acid

Answer 27

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

Question 28

*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

Answer 28

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

Question 29

Why is Ti used in hip replacement surgery?

Answer 29

Low reactivity & low density

Question 30

State equation for Stage 1 of Kroll process

Answer 30

TiO2 + 2Cl2 + 2C = TiCl4 + CO2

Question 31

Equation for Stage 2 of Kroll process

Answer 31

Magnesium: TiCl4 + 2Mg = Ti + 2MgCl2 Sodium: TiCl4 + 4Na = 4NaCl + Ti

Question 32

In stage 1 titanium is converted into…

Answer 32

TiCl4

Question 33

In stage 2 titanium is reduced by…

Answer 33

Magnesium & sodium

Question 34

What is the ore of titanium called?

Answer 34

Rutile

Question 35

What is the formula of titanium (IV)?

Answer 35

TiO2

Question 36

Which gas prevents reaction w/ O2 or nitrogen

Answer 36

Argon ~ prevents titanium becoming brittle & oxidation of Ti

Question 37

What is titanium IV oxide heated up w/?

Answer 37

Chlorine gas & coke

Question 38

Why is Ti used in aircraft?

Answer 38

It has Low Density

Question 39

Name the Bayer process

Answer 39

- 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!

Question 40

What is sodium hydroxide?

Answer 40

An alkali

Question 41

Why does alumina react w/ sodium hydroxide?

Answer 41

Alumina reacts w/ it because it’s amphoteric

Question 42

Write the balanced equation for bayer process

Answer 42

2Al (OH)3 ---> Al2O3 + 3H2O

Question 43

name two correctly balanced equations forming alkalis

Answer 43

CaO + H2O ---> Ca(OH)2 Na2O + H2O ---> 2NaOH

Question 44

Definition of Electrolysis