Developing metals

Question 1

What is oxidation?

Answer 1

A loss of electrons

Question 2

What is reduction?

Answer 2

A gain of electrons

Question 3

What is a reducing agent?

Answer 3

Donates electrons

Question 4

What is an oxidising agent?

Answer 4

Takes/accepts electrons

Question 5

Does an oxidising agent lose or gain electrons during a redox reaction?

Answer 5

Gain

Question 6

Does a reducing agent lose or gain electrons during a redox reaction?

Answer 6

lose

Question 7

Apart from multiplying up the reactants and products, name three things you can add to balance a half equation.

Answer 7

H+ ions
Electrons
Water

Question 8

What are acid base titrations used for?

Answer 8

To find how much acid is needed to neutralise a base

Question 9

In an acid base titration what goes into the burette?

Answer 9

The acid

Question 10

What is the purpose of a redox titration?

Answer 10

How much oxidising agent is needed to react with a quantity of reducing agent

Question 11

What is a common oxidising agent used in redox titrations?

Answer 11

manganate(VII) ions

Question 12

How do you do a redox titration?

Answer 12

1) Measure quantity of reducing agent using pipette and put in conical flask
2) Add dilute sulfuric acid in excess to conical flask
3) Add oxidising agent to the burette
4) Swirl the conical flask as you add it
5) Stop when you reach end point
6) repeat until concordant titrations

Question 13

In a redox reaction what goes in the burette?

Answer 13

The oxidising agent

Question 14

Why do you add dilute sulfuric acid to the conical flask in a redox titration?

Answer 14

The acid is added to make sure there are plenty of H+ to allow the oxidising agent to be reduced

Question 15

What is the colour change in a redox reaction using potassium manganate(VII)?

Answer 15

colourless –> pink end point

Question 16

What are the reactions in an electrochemical cell?

Answer 16

oxidation and reduction

Question 17

What reaction happens at the anode in an electrochemical cell?

Answer 17

oxidation

Question 18

What reaction happens at the cathode in an electrochemical cell?

Answer 18

reduction

Question 19

What does an electrochemical cell consist of?

Answer 19

two different metals dipped in salt solutions of their own ion and connected by a wire and a salt bridge

Question 20

What direction do electrons flow through a wire in an electrochemical cell?

Answer 20

from the most reactive metal to the least reactive metal

Question 21

What is cell potential?

Answer 21

The voltage between the two half-cells

EMF Ecell

Question 22

What electrode do you need when the half cell consists of two aqueous solutions of the same element?

Answer 22

Needs to conduct electricity but be very inert

eg.platinum or graphite

Question 23

How do you set up an electrochemical cell?

Answer 23

1) Clean surface of strip of metals you’re using as electrodes with sand paper
2) Clean electrodes using propanone
3) Place electrode into beaker filled with solution containing ions of that metal
4) Create a salt bridge by dipping a piece of filter paper in salt solution and then drape it between the two beakers
5) connect electrodes with voltmeter crocodile clips and wires

Question 24

Does the reaction go forwards at the half cell if the electrode potential is more or less positive?

Answer 24

more positive

Question 25

What happens at the half cell with a more negative electrode potential?

Answer 25

it is oxidised so goes backwards

Question 26

What are standard conditions for electrode potentials?

Answer 26

298K 100kPa 1.00 moldm^-3

Question 27

What are electrode potential measured against?

Answer 27

Stand hydrogen electrodes

Question 28

What is standard electrode potential?

Answer 28

Voltage of half cell measured under standard conditions when half cell is connected to a standard hydrogen potential

Question 29

What is the equation for Ecell?

Answer 29

Ecell = (E more positive) - (E more negative)

Question 30

Do more reactive metals have more negative or positive electrode potentials?

Answer 30

more negative

Question 31

Why do more reactive metals have more negative electrode potentials?

Answer 31

more likely to lose electrons to form a positive ion

Question 32

Do less reactive metals have more negative or positive electrode potentials?

Answer 32

more positive

Question 33

Why do less reactive metals have more positive electrode potentials?

Answer 33

more likely to gain electrons to form a negative ion

Question 34

How can you tell if a reaction is feasible, at standard conditions, using electrode potentials?

Answer 34

Use them to calculate Ecell | if Ecell is positive it is feasible if it is negative it is not

Question 35

What is the voltage of the standard hydrogen electrode half-cell?

Answer 35

0.00V

Question 36

Why is rust less likely under alkaline conditions?

Answer 36

OH- ions added means 2(H2O) + O2 +4e- --> 4OH- is shifted to left to so more electrons produced so Fe2+ + 2e- --> Fe Shifts to the right to balance this so less Fe2+ to form Fe(OH)2

Question 37

What are the half equations in the start of rusting of Fe?

Answer 37

Fe2+ + 2e- --> Fe | 2(H2O) + O2 +4e- --> 4OH-

Question 38

What equations show how Fe2+ react to make Fe(OH)3 in the process of rusting?

Answer 38

Fe2+ +2OH- --> Fe(OH)2 | 2(H2O) + O2 + 4Fe(OH)2 --> Fe(OH)3

Question 39

What is rust?

Answer 39

Fe2O3 xH2O

Question 40

What was rust before it became hydrated iron(III) oxide?

Answer 40

iron(III) hydroxide | Fe(OH)3

Question 41

How do you prevent rusting?

Answer 41

Barrier | Sacrificial metal

Question 42

What are two examples of the barrier method of rust prevention?

Answer 42

- Coating with a polymer (Painting) | - Oiling or greasing

Question 43

When would you use oiling or greasing to prevent rust?

Answer 43

When moving parts are involved

Question 44

What is the sacrificial method?

Answer 44

Placing a more reactive metal with the iron so the water and oxygen react with that metal instead

Question 45

What sacrificial metal is most often used? Why?

Answer 45

Zinc | It has a more negative electrode potential than Fe so it will be oxidised instead

Question 46

What is galvanising?

Answer 46

Coating something zinc

Question 47

What two substances react with iron to produce rust?

Answer 47

Water and Oxygen

Question 48

What is a complex ion?

Answer 48

A central metal ion surrounded by datively bonded ligands

Question 49

What is a dative covalent bond?

Answer 49

Both shared electrons come from the same atom

Question 50

In a complex where do the shared pair of electrons in the dative bond come from?

Answer 50

The ligands

Question 51

What is a ligand?

Answer 51

Something that donates a pair of electrons to a central transition metal ion to form a dative bond

Question 52

What is a monodentate ligand?

Answer 52

Has one lone pair of electrons

Question 53

What is a bidentate ligand?

Answer 53

Has two lone pairs of electrons

Question 54

What is a polydentate ligand?

Answer 54

Has multiple lone pairs of electrons

Question 55

What is are four examples of monodentate ligands?

Answer 55

H2O NH3 CN- halide ions

Question 56

What is an example of a bidentate ligand?

Answer 56

ethanedioate

Question 57

What is the coordination number?

Answer 57

The number of dative bonds formed with ligand

Question 58

What shape would a molecule with a coordination number of 6?

Answer 58

Octahedral

Question 59

What two shapes would a molecule with coordination number of 4 have?

Answer 59

Tetrahedral | Square planar

Question 60

What size bond angles does an octahedral complex have?

Answer 60

90 degrees

Question 61

What size bond angle does a tetrahedral shape have?

Answer 61

109.5 degrees

Question 62

What size bond angle does a square planar shape have?

Answer 62

90 degrees

Question 63

How do ligands affect the 3d sub-shell of transition metal ions?

Answer 63

Split it into two energy levels because some orbitals gain energy

Question 64

When will the compound look colourless or white? why?

Answer 64

If the 3d sub shell is full or empty | because the electrons won't jump up to higher orbitals

Question 65

What do you mix with aqueous transition metal ions for them to become coloured?

Answer 65

NaOH or NH3 to make a coloured hydroxide precipitate

Question 66

What is ligand substitution? what does it cause?

Answer 66

One ligand being swapped for another | a colour change

Question 67

Why do transition metal compounds make good catalysts

Answer 67

They can change oxidation states by gaining or losing electrons in their D orbitals so they can transfer electrons to speed up reactions

Question 68

Why can transition metal compounds cause health risks?

Answer 68

Their compounds can be toxic

Question 69

Stages of heterogeneous catalysis

Answer 69

1. Adsorption 2. Bonds in molecule break 3. New bonds form 4. desorption

Question 70

What makes a good heterogeneous catalyst?

Answer 70

Attract the reactant strong enough so it is held to the surface long enough to bond but not too strong it won't desorb

Question 71

What is a heterogeneous catalyst?

Answer 71

A catalyst in a different state to the reactants

Question 72

What is a homogeneous catalyst?

Answer 72

A catalyst in the same state as the reactant

Question 73

How does a homogeneous catalyst work?

Answer 73

Combine with reactants to form intermediate species which then reacts to form products and reform the catalyst

Question 74

What happens to white light that makes a transition metal ion colour?

Answer 74

One frequency of light is absorbed | the rest are transmitted (the colour you see)

Question 75

How do you set up a colorimeter?

Answer 75

1. Pick a filter that is a colour that's absorbed 2. Set zero using a blank sample 3. Place sample in a cuvette and measure

Question 76

What does a high absorbance on the colorimeter mean?

Answer 76

Very concentrated

Question 77

What is monochromatic light?

Answer 77

light of a single colour