Chemistry June exams

Question 1

what is the order of metals reactivity? least to most

Answer 1

gold
sliver
copper
iron
(carbon)
aluminium
magnesium
calcium
sodium
potassium

Question 2

what is the method of extraction for potassium, sodium, calcium, magnesium, aluminium

Answer 2

electrolysis of the metal ore

Question 3

what is a metal ore?

Answer 3

a rock that contains metal oxides

Question 4

what is the method of extracting zinc, iron, copper?

Answer 4

heat the metal oxide with carbon as carbon is more reactive. the metal is obtained

Question 5

what is the method of extraction for silver and gold?

Answer 5

found uncombine. the metal is found by itself

Question 6

what is the reaction of water like with potassium, sodium and calcium

Answer 6

react with cold water to form H2 (g) and metal hydroxide

Question 7

what is the reaction of water like with magnesium, aluminium, zinc and iron?

Answer 7

react very slowly with cold water. react with steam forming H2 and metal oxide

Question 8

what is the reaction with water like with copper, silver and gold?

Answer 8

do not react with cold water or steam

Question 9

what is the reaction with dilute acid like with potassium and sodium?

Answer 9

violent reaction

Question 10

what is the reaction with dilute acid like with calcium, magnesium, aluminium?

Answer 10

react to form hydrogen and a salt solution

Question 11

what is the reaction with dilute acid like with zinc and iron?

Answer 11

react to form hydrogen and a salt solution

Question 12

what is the reaction with dilute acid like with copper, silver and gold?

Answer 12

do not react

Question 13

define corrosion

Answer 13

happens when a metal reacts with oxygen making the metal weaker over time. the metal is oxidised

Question 14

define rusting

Answer 14

only applies to IRON! iron requires water as well as oxygen

Question 15

define tarnish

Answer 15

metals that are quite reactive would be expected to corrode quickly, however, they do not corrode because their surfaces form a protective oxide layer, which prevents further reaction

Question 16

what are the different steps of the life cycle assessment

Answer 16

1- extracting and processing raw materials
2- manufacturing and packaging
3- use and operation during its lifetime
4- disposal at the end of its useful life

Question 17

what are the physical properties of the transition metals?

Answer 17

-high melting/boiling point
-malleable
-ductile
-good conductors of electricity
-shiny when polished, remove the corroded layer

Question 18

define malleable

Answer 18

hammered into shape

Question 19

define ductile

Answer 19

drawn into wires

Question 20

why are transition metals good conductor of electricity?

Answer 20

due to the free moving delocalised electorons

Question 21

what are the chemical properties of the transition metals?

Answer 21

-form coloured complexes/substances
-used as catalysts
-reactivity(not as reactive as group 1 or 2)

Question 22

how are transition metals used as catalysts?

Answer 22

-speed up the rate of reaction, their mass remains unchanged
-they work by lowering the activation energy and provide an alternative energy pathway

Question 23

what are the ways we can prevent rusting?

Answer 23

-store metal in an unreactive atmosphere (nitrogen or argon) to prevent oxygen from air reacting
-keep water away by using a DESICCANT powder that absorbs water vapour
-paint the metal/grease/oil

Question 24

what is sacrificial protection

Answer 24

a piece of magnesium is attached to the iron or steal object. Mg/Zn will oxidise easier and will react before the iron. This protection lasts until the sacrificial metal erodes away

Question 25

what is an example of a sacrificial metal?

Answer 25

-a ships outer hull (bottom of ship) will have a sacrificial metal on it

Question 26

what does electroplating do

Answer 26

-coats the surface of one metal with another. Improves resistance to corrosion. Also improves the appearance

Question 27

what is needed to carry out electrolplating

Answer 27

-an anode (made from the plating metal) -an electrolyte, solution containing ions of the plating metal -a cathode, the metal object itself

Question 28

what is electroplating

Answer 28

-get a silver plating metal and a copper ring and put it in an electrolyte -connect them to a direct current supply

Question 29

what happens to the silver in electroplating

Answer 29

-oxidation -loses electrons

Question 30

what happens to the copper ring in electroplating

Answer 30

-reduction -gains e;ectrons

Question 31

what is galvanising

Answer 31

iron and steel objects can be protected from rusting by coating them with zinc

Question 32

how does zinc improve resistance to corrosion

Answer 32

-its stops 02 reacting with iron in steel and zinc acts as a sacrificial metal

Question 33

how can galvanising be carried out

Answer 33

-using electroplating or by dipping the object in molten zinc

Question 34

what are some examples of galvanising

Answer 34

-food cans, made of steel and electroplated with tin -tin does not react with O2 in air and H2O at room temperature -tin stops air and H2O reacting with the iron in steel -if the tin layer is damaged, the iron in steel can react faster and iron is more reactive than tin, therefore iron acts as a sacrificial metal

Question 35

define alloys

Answer 35

a mixture of a metal element and one or more other elements

Question 36

what is the characteristic of a pure metal

Answer 36

all metal cations are arranged in a lattice and layers can slide over each other as cations are the same size

Question 37

what is the characteristic of alloys

Answer 37

hard for the layers to slide over each other, due to different size of atoms/cations

Question 38

what are the examples of alloys?

Answer 38

-Wrought iron -stainless steel -tool steel -mild steel -stronger steels

Question 39

what is wrought iron

Answer 39

iron with less than 0.08% carbon

Question 40

what is stainless steel

Answer 40

-resist rusting -contains chromium which reacts with O2 and a layer of Cr2O3 forms and is thick enough to stop air and H2O reacting with the iron in steel. -if forms a transparent layer. -if the metal scratches, chromium reacts

Question 41

what is tool steels

Answer 41

contains tungsten and molybdenum: drill bits

Question 42

what is mild steel

Answer 42

low carbon content but contains manganese to increase strength and maintain malleability. used for building materials.

Question 43

what are stronger steels

Answer 43

difficult to press into shape but car manufacturers use them to produce strong but relatively high weight car bodies.

Question 44

what are the biological methods of metal extraction

Answer 44

-bioleaching -phytoextraction

Question 45

what is bioleaching

Answer 45

-uses bacteria grown on a low grade ore. the bacteria produce a solution containing copper ions called a leachate. copper is extracted from the leachate by displacement using scrap ion, then purifies by electrolysis.

Question 46

what is phytoextraction

Answer 46

involves growing plants that absorb metal compounds. the plants ate burnt to form ash, from which the metal is extracted

Question 47

what are the advantages of both bioleaching and phytoextraction

Answer 47

-no harmful gases are produced -causes less damage to the landscape than mining -conserves supplies of higher grade ores

Question 48

what are the disadvantages of both bioleaching and phytoextraction

Answer 48

very slow

Question 49

what are the advantages of bioleaching

Answer 49

does not require high temperatures

Question 50

what are the disadvantages of bioleaching

Answer 50

toxic substances and sulfuric acid can be produced by the process and damage the environment

Question 51

what are the advantages of phytoextraction

Answer 51

can extract metals from contaminated soils

Question 52

what are the disadvantages of phytoextraction

Answer 52

-more expensive than mining some ores -growing plants is dependent on weather conditions