Stoichemetry

Question 1

What is a titration reaction

Answer 1

A titration is a technique where a solution of known concentration is used to determine the concentration of an unknown solution. Typically, the titrant (the know solution) is added from a buret to a known quantity of the analyte (the unknown solution) until the reaction is complete.

Question 2

Chromatography is used in the what what and what of components in a mixture

Answer 2

Separation, purification and identification

Question 3

What is chromatography paper made of

Answer 3

Cellulose fibres, insoluble carbohydrates with OH that water bonds to

Question 4

What does chromatography paper comprise in paper chromatography

Answer 4

Stationary phase

Question 5

What happens to the substance which is analysed in chromatographic analysis first

Answer 5

Dissolved into a suitable solvent and spotted onto stationary phase

Question 6

What does the movement of compounds in chromatography depend on

Answer 6

Their polarity eg more polar substances will be attracted to the polar -OH group

Question 7

What is the formula for energy released and what is the units

Answer 7

M(water) x 4.18 x Delta T

Joules

Question 8

How to convert joules to kilojoules

Answer 8

Divide by 1000

Question 9

Two approximations in combustion reactions

Answer 9

That the density of the solution is the same as the density of water
The specific heat of the solution is equal to the specific heat of water

Question 10

3 assumptions of combustion reactions

Answer 10

Any temp change is instantaneous
No heat is lost or gained
All of any solid is dissolved

Question 11

3 reasons in ethanol combustion etc the value is lower than the true value

Answer 11

Heat is lost to surroundings
Ethanol evaporates on wick
Incomplete combustion

Question 12

Why are polystyrene cups used in combustion reactions

Answer 12

Good insulator and doesn’t react with liquids

Question 13

Why is stirring carried out

Answer 13

Ensures complete and fast reaction to minimise heat lost also ensures even distribution of heat

Question 14

What are fuels

Answer 14

Substances that releases heat energy when burnt or combusted

Question 15

3 types of fossil fuels

Answer 15

Coal, gas, oil

Question 16

3 biofuels

Answer 16

Ethanol (fermentation)
Biodiesel
Biogas

Question 17

3 advantages of biofuels

Answer 17

Plant based hence renewable, carbon neutral (no NET change in CO2 levels), less emissions

Question 18

3 disadvantages of biofuel

Answer 18

Biodiesel conceals at very low temperatures
Land is cleared to grow crops to produce leading to higher food prices
Fossils fuels are used to manufacture biofuels

Question 19

What is the energy conversion in galvanic cells

Answer 19

Spontaneous chemical reactions that produce chemical energy

Question 20

In a copper aluminium galvanic cell what are three observations

Answer 20

Copper deposit at cathode
Fading of blue Colour
Al corrosion

Question 21

In a copper aluminium galvanic cell why is aluminium the anode

Answer 21

Because it is more reaction and therefore oxidises which always occurs at the cathode

Question 22

What is the electron flow in galvanic cells

Answer 22

More to less reactive electrode

Question 23

In galvanic cells where do the anions and cations go

Answer 23

Anions -> anode

Cations -> cathode

Question 24

What are fuel cells

Answer 24

A special type of voltaic cell

Question 25

In a fuel cell does oxygen react at the anode or cathode

Answer 25

Cathode as its been reduced

Question 26

Reduction reaction in fuel cells with oxygen

Answer 26

O2 + 4H^+ + 4ē -> 2H2O

Question 27

Oxidation reaction in fuel cells with methane

Answer 27

CH4 + 2H2O -> CO2 + 8H^+ + 8ē

Question 28

What is an electrolytic cell

Answer 28

Cell that converts electrical energy to chemical energy using a power supply

Question 29

Two reactions for the electrolysis of water

Answer 29

Oxidation - 2H2O -> O2 + 4H^+ + 4ē | Reduction - 2H2O + 2ē -> H2 + 2OH^-

Question 30

In a car battery during discharge what type of cell is it

Answer 30

VOLTAIC

Question 31

In a car battery during recharging what type of cell is it

Answer 31

ELECTROLYTIC

Question 32

Why are most metals found combined with other metals

Answer 32

Most metals are reactive and have the tendency to lose electrons

Question 33

Two forms of metal production

Answer 33

Chemical reduction and electrolysis

Question 34

Formula for electrolysis in the production of aluminium

Answer 34

Al3^+ + 3ē -> Al

Question 35

4 steps of the production of zinc

Answer 35

1) Ore is crushed to fine dust 2) Mineral is dried and roasted in air 3) ZnO is dissolved in H2SO4 4) Electrolysis of ZnSO4 (Zn^2+ + 2ē -> Zn) to produce Zinc metal

Question 36

Why and how are metal ions such as Pb2+ and Cd2+ removed during zinc production

Answer 36

Displacement using Zn, removed as they would be preferentially reduced during electrolysis

Question 37

In zinc production what is the byproduct of SO2 used for

Answer 37

Used to make sulphuric acid

Question 38

What is dynamic equilibrium

Answer 38

Reaction continues with no net change

Question 39

What is the significance of Kc

Answer 39

If the Kc is large it favours the forward reaction and if it is small if favours the back reaction

Question 40

4 ways to increase yield in the haber process

Answer 40

High pressure Low temperature Increased N2 / H2 Remove ammonium as it's produced

Question 41

What is the catalyst in the haber process

Answer 41

Iron powder

Question 42

How to convert kJmol^-1 to kJg^-1

Answer 42

Divide by molar mass of specified reactant

Question 43

Equation for heat energy released or absorbed

Answer 43

n x molar enthalpy of reaction (q x n x delta H

Question 44

What does q stand for

Answer 44

Heat energy transferred

Question 45

2 sources of systematic error in combustion

Answer 45

Not all of the heat energy released is absorbed by the water Combustion is incomplete as portion of alcohol undergoes incomplete combustion

Question 46

2 sources of random errors in combustion

Answer 46

Measuring cylinder doesn't not have high resolution | Flame wasn't concentrated at the same point throughout the experiment due to draughts

Question 47

How to achieve delta H values of a higher accuracy

Answer 47

Use a bomb calorimeter

Question 48

4 steps when using polystyrene cup

Answer 48

Measure out

Question 49

What factor effects Kc

Answer 49

Temperature

Question 50

2 ways to save energy costs in production

Answer 50

Catalyst | Run process continually

Question 51

What's the charge of the anode and cathode in galvanic (voltaic) cells

Answer 51

Anode Negative | Cathode positive

Question 52

What's the charge of the anode and cathode in electrolytic cells

Answer 52

Anode positive | Cathode negative

Question 53

Oxidation is a ... In oxidation number

Answer 53

Increase

Question 54

Reduction is a. ... In oxidation number

Answer 54

Decrease

Question 55

In half cells will the more reactive metal become the anode or cathode

Answer 55

Anode

Question 56

The direction of movement of cations in the salt bridge will be towards?

Answer 56

The cathode

Question 57

The direction of movement of anions in the salt bridge will be towards the?

Answer 57

Anode

Question 58

3 advantages of fuel cells

Answer 58

They continuously produce an electric current so long as fuel and oxidant is continuously supplied They have a high operating efficiency Do not produce pollutant gases Electrodes and electrolyte are not consumed during operation

Question 59

3 disadvantage of fuel cells

Answer 59

High purity fuels and oxidants are costly Medium to high temperatures are needed for the cells to function most effectively Metal electrode catalysts such as platinum and palladium are very costly

Question 60

In exothermic reactions in energy profile diagrams is the bump near the left or the right

Answer 60

Left

Question 61

In endothermic reactions in energy profile diagrams is the bump near the left or the right

Answer 61

Right

Question 62

6 factors that effect reaction rate

Answer 62

``` Concentration of reactants Pleasure Temperature of reaction mixture Surface area of solid reactants Catalysts Intensity of light for photochemical reactions ```

Question 63

What conditions are needed for a reversible chemical reaction to reach equilibrium

Answer 63

A closed system that's at a constant temperature

Question 64

What is Le châtelier's principle

Answer 64

If an external change is made to the reaction conditions of a system at equilibrium so that it is no longer at equilibrium a net reaction will occur in the direction that counteracts the change

Question 65

According to Le Chateliers principle what will happen if the concentration of a reactant is increased

Answer 65

Equilibrium shifts to the right

Question 66

According to Le Chateliers principle what will happen if the concentration of the reactants decreases

Answer 66

Equilibrium shifts to the left

Question 67

According to Le Chateliers principle what will happen if the concentration of the products increases

Answer 67

The equilibrium shifts to the left

Question 68

According to Le Chateliers principle what will happen if the concentration of the products decreases

Answer 68

The equilibrium shifts to the right

Question 69

What's froth floatation

Answer 69

Powder from the grinding mill is mixed with water in large floatation tanks to form a slurry . Frothing agents such as pine oil are added with water soluble substances called collectors, air is blown through aqueous suspension of ground ore

Question 70

Why is froth floatation Carried out

Answer 70

To concentrate desired minerals

Question 71

What a are commonly used collectors referred to as

Answer 71

Xanthates

Question 72

Describe the structure of a xanthate ion

Answer 72

Ionic head and non polar tail

Question 73

4 steps in producing zinc

Answer 73

Roasting zinc sulfide Leaching zinc oxide Purification of zinc surface Electrolysis

Question 74

The degree of difficulty of reduction to the metal increases as the ... Increases

Answer 74

Reactivity of the metal