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TEST Flashcards

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1
Q

Describe an experiment to determine the empirical formula for a compound

A

Weigh crucible
Put a sample of magnesium into the crucible and weigh it.
Calculate the mass of magnesium by subtracting the mass of the empty crucible
Heat over Bunsen burner
Carefully lift lid from time to time to allow some oxygen into the crucible for the magnesium to fully oxidise without letting any magnesium oxide escape.
Heat until mass of crucible it at its max
Repeat step 2
To find ep formula you need mass of magnesium and mass of oxygen- to find mass of oxygen atoms subtract the mass of magnesium used from the mass of magnesium oxide.
Divide two masses by relative atomic masses and simplify.

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2
Q

What is a mole of particles

A

One mole is the Avogadro number of particles (atoms, molecules, ions or electrons) in a substance.

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3
Q

What is the mass of a product formed in a reaction controlled by?

A

The mass of reactant that is not in excess

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4
Q

State the meaning of the term ‘electrolyte’

A

An ionic substance/liquid with freely moving ions that electrolysis takes place in

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5
Q

What happens in electrolysis? (SUMMARY!!!!!)

A

The process of using electricity to break apart the ions in an ionic substance that is either dissolved in water or molten.

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6
Q

Explain the movement of ions during electrolysis

A

Positively charged ions move to the negative electrode (CATHODE) during electrolysis. They gain electrons and are reduced.
Negatively charged ions move towards the positive electrode (ANODE) during electrolysis. They lose electrons and are oxidised.

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7
Q

What happens to the electrons in oxidation

A

Electrons are lost (+ charge)

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8
Q

What happens to the electrons in reduction

A

Electrons are gained (- charge)

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9
Q

Where does oxidation occur

A

At the anode

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10
Q

Where does reduction occur

A

At the cathode

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11
Q

Recall the products formed from the electrolysis of a variety of common compounds and solutions

A 
Copper chloride solution
Sodium chloride solution
Sodium Sulphate solution 
Acidified water 
Molten lead
Bromide
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12
Q

HOW TO REMEMBER the order of the reactivity series from most reactive downwards

A

People Say Little Children Make A Zebra Ill Constantly Sniffing Giraffes.

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13
Q

Why are displacement reactions redox reactions

A

displacement reactions are when more reactive elements replace other elements in a compound, Redox means reduction/oxidation (having to do with reactivity and electron transfer)

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14
Q

what is a cation

A

a positively charged ion which would be attracted to the cathode

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15
Q

recall meaning of the term ORE

A

naturally occurring rocks that contain metal or metal compounds in sufficient amounts to extract them.

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16
Q

Recall some metals that are found uncombined in the earths crust

A

GOLD
SILVER
COPPER
(LESS REACTIVE)

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17
Q

How and why are some metals extracted from their ores by heating carbon

A

Less reactive metals such as iron are extracted by reduction with carbon. The metal oxide loses oxygen, and therefore is reduced. The carbon gains oxygen and therefore is oxidised

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18
Q

Explain how and why some metals are extracted from their ores by electrolysis

A

More reactive metals such as aluminium are extracted by electrolysis.

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19
Q

Oxidation in terms of oxygen

A

The addition of oxygen to a substance in a reaction, or the reaction of a substance with oxygen

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20
Q

How are all metals extracted

A

by reduction of their ores

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21
Q

Advantages and disadvantages of recycling a metal

A

Helps limit amount of metals that must be produced
SUSTAINABLE
Process of recycling metals usually creates much less pollutants
and uses less energy therefore less fossil fuels are being burnt
HOWEVER
Can be expensive
Time consuming
Requires energy

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22
Q

How do we recycle plastic

A

Sorting it into different polymers and then chipping it and melting i- re shaping and molding it

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23
Q

Pros and Cons of recycling

A 
Reduces pollution 
Reduces global warming
Reduce energy usage
Be sustainable 
However 
High in cost
Recycling sites can be unsafe, unsightly and unhygienic
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24
Q

What happens in reversible reactions

A

The products can react to produce the original reactants again

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25
Q

⇄ (Use of the symbol in chemical equations)

A

Shows the reaction goes both ways

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26
Q

What is dynamic equilibrium

A

Both the backwards and forwards reactions occur but the substances are in balance

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27
Q

Describe the formation of Ammonia

Also known as the haber process

A

Nitrogen from the air reacts with hydrogen derived mainly from natural gas (methane) into ammonia.
This reaction is reversible and exothermic

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28
Q

Recite the equation for Ammonia creation

A

N2 + 3H2 ⇄ 2NH3 (+heat)

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29
Q

Recite the 3 conditions used in the Haber process

A

450*
200 atmosphere pressure
Iron catalyst

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30
Q

Uses of Haber processes

A

Fertilizers
Explosives
Cleaning fluids

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31
Q

Changes in pressure will not affect the position of equilibrium if…

A

the number of moles of gases on both sides of equation are equal

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32
Q

How does changes temperature effect equilibrium

A

Increasing the temperature always favours the endothermic reaction.Decreasing the temperature always favours the exothermic reaction.

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33
Q

Describe the difference between endothermic and exothermic

A

Endothermic- requires energy

Exothermic- gives out/releases energy

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34
Q

What is LCA

A

A life cycle assessment –is used to work out the environmental impact of a product from the raw materials to dispose of the product

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35
Q

Describe the position of transition metals in the periodic table

A

In the center of the periodic table between groups 2 and 3

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36
Q

What are the chemical and physical properties of transition metals

A

Chemical- Acts as a catalyst and forms a colored compound and has variable oxidation states
Physical- High density and high melting points

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37
Q

Why has iron got typical properties of a transition metal

A

High density - 7.8
High melting point- 1538*
Uses as a catalyst- haber process

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38
Q

What is corrosion of metals a result of

A

oxidation

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39
Q

How does rusting of iron occur

A

When iron is exposed to oxygen and moisture for a long period of time
Over time, the oxygen combines with the metal at an atomic level forming a new compound oxide

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40
Q

How does sacrificial protection work

A

Covering the object with a thin layer of zinc (sacrificial metal), this stops the oxygen and water reaching the metal underneath. The zinc is more reactive than iron, so it oxidises in preference to the iron object

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41
Q

Why do metal objects need to become electroplated

A

increases life of metal

prevent corrosion

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42
Q

Recall some common examples of electroplating

A 
Copper
Nickel 
Tin
Zinc
Gold 
Silver
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43
Q

Recall the name of a common alloy

A

steel

an alloy of iron and carbon

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44
Q

What is an alloy

A

A mixture of a metal element with one or more other elements (usually metals)

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45
Q

What happens in alloying

A

Within the mixture of two or more elements, where at least on element is a metal (the alloy) Alloys contain atoms of different sizes, which distort the regular arrangement of atoms. This makes it more difficult for the layers to slide over each other, so alloys are harder than the pure metal

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46
Q

Why is iron alloyed with other metals

A

Pure iron is to soft for many uses

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47
Q

Common uses for Aluminium, copper and gold

A

Aluminum- bodies of planes
Copper- Electrical wires as its a good conductor
Gold- Jewelry (lack of reactivity)

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48
Q

Common alloys that contain aluminum or copper

A

Duralium (contains both)
Bronze- copper+tin
Brass-copper+zinc

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49
Q

Difference between empirical formula and molecular formula

A

Empirical formula tells you the simplest or most reduced ratio of elements in a compound. WHEREAS molecular formula tells you how many atoms of each element are in a compound

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50
Q

Describe a closed system

A

Same mass after as before the reaction

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51
Q

Describe a open system

A

Same mass but if it’s a gas it seems like there’s a loss

52
Q

Describe methods of metal extraction

A

Bioleaching -using bacteria, absorb copper through its roots, extracted by displacement and purify by electrolysis.

Phytomining- using plants- plants absorb copper- burn plants - H2SO4

53
Q

Explain how a elements reactivity is related to its resistance to oxidation

A

The more reactive a metal is the quicker it oxidises eg- a slice of potassium will become dull as it quickly reacts with oxygen, whereas less reactive metals such as gold remain shiny that’s why they are used to make jewellery

54
Q

What is a redox reaction

A

A reaction in which both oxidation and reduction occur

55
Q

Why are alloys often stronger than the metals they contain

A

They distort the arrangement so the layers don’t slide past eachother as easily

56
Q

Closed

A

You will always have the same mass before and after a reaction

57
Q

How to find empirical formula

A

Mass
Mass / mr
Divide by smallest

58
Q

How to calculate relative formula mass (or Mr)

A

Add relative atomic mass for all atoms shown in its chemical formula e.g.-
Find Mr of H20

Ar of H= 1 O= 16
Mr of H2O = 1+1+16 = 18

59
Q

What is Ar

A

Relative atomic mass of an atom in the periodic table eg Oxygen = 16

60
Q

What is Mr

A

Relative formula mass

All atomic masses added together

61
Q

How calculate mass of product/reactant

A

Find out if you’re being asked to find the mass of product OR reactant

If reactant = Mr of reactant / Mr of product

If product = Mr product / Mr reactant

Then Multiply by known mass

62
Q

Formula triangle for calculating concentrations of solutions in g dm3

A

Mass (solute in g)

          Conc              Vol (solution in dm3)
63
Q

Converting dm3 to cm3

A

Cm3-dm3 (divide by 1000)

Dm3-cm3 (multiply by 1000)

64
Q

Formula triangle for number of moles

A

Mass

Ar or Mr                               Moles
65
Q

Formula triangle for number of particles in a substance

A

Particles

    Moles Number            Avo no
66
Q

What are positive ions also known as

A

Cations

67
Q

What are negative ions also known as

A

Anions

68
Q

In purification of copper how do we figure out which element will under go (reduction or oxidation)
or which one will be discharged
AT THE CATHODE CONCERNING H+ IONS

A

If it is less reactive than hydrogen it will be discharged and under go reduction or oxidation
If it is more reactive than hydrogen then hydrogen will take its place

69
Q

In purification of copper how do we figure out which element will under go (reduction or oxidation)
or which one will be discharged AT THE ANODE CONCERNING OH- IONS

A

In dilute conditions OH- (hydroxide) will be discharged

But if In a concentrated solution then the halites will be discharged instead of OH-

70
Q

Where do OH- and H+ ions go in solutions

A

H+ goes to the negative cathode

OH- goes to the positive anode

71
Q

How does the electrolysis of copper Sulfate solution using copper electrodes can be used to purify copper

A

The positive anode is made of impure copper which is to be purified. The negative cathode is a bar of pure copper. The two electrodes are placed in copper(||) sulfate.
The copper ions leave the anode and are attracted to the cathode, where they are deposited as copper atoms. The pure copper cathode increases gently in size, while the anode decreases.p

72
Q

what happens to an element when it loses an electron

A

It has a positive charge

73
Q

What happens to an element when it gains an electron

A

It has a negative change

74
Q

What’s an oxidation number

A

The different charges and number charges of atoms

75
Q

If in the half equation u have lost an electron how do u write it

A

You can’t use a - sign therefore u have to write the +e but at the end!
E.g.
Na– Na+ +e

76
Q

Half equation for copper purification

A

Cu—Cu2+ + 2e

77
Q

What is corrosion

A

Rusting of a metal

78
Q

What would happen in the haber process of the atmospheric pressure was increased

A

A high pressure would increase the percentage yield of ammonia but very high pressures are expensive

79
Q

What would happen in the haber process if temperature was increased

A

It would cause a faster reaction but decrease the percentage yield of ammonia

80
Q

What are the 2 half equations for lead and bromide

A

Lead –
Pb2+ + 2e- —-> Pb (reduction)

Bromide
2Br —-> Br2 + 2e-

81
Q

Explain what happens in electrolysis of molten lead bromide

A

Positive lead ions are attracted to negative cathode and are discharged to form molten lead.
The negative bromide ions are attracted to the positive anode electrode and discharged to form bromine vapour.
The products of this electrolysis are lead metal and bromine.

82
Q

How will the rate of equilibrium change if you change temperature

A

If temperature is increased the reaction will shift to favour the endothermic reaction to remove extra heat added.
Increase temp= favours endothermic reaction
Decreasing temp= favours exothermic reaction

83
Q

How will the rate of equilibrium change if you change pressure

A

High pressure= favours side with lowest volume of gases

Low pressure= favours side with the highest volume of gases

84
Q

Changes in pressure won’t effect position of equilibrium if…

A

Number of moles of gas on each side of the equation is equal.

85
Q

How will the rate of equilibrium change if you change the concentration

A

Increase conc of reactants- equilibrium will move to right to use up reactants (makes more products)
Increase conc of products- equilibrium will move to left to use up products (makes more reactants)

86
Q

How will the rate of equilibrium change if you use a catalyst

A

Reduces time taken to reach equilibrium but doesn’t change position of equilibrium because it increases rates of forward and reverse reactions by the same amount.

87
Q

What is a rule in equilibrium

A

Any change made to a reaction which is in equilibrium will result in the equilibrium position moving to minimise Change made.
Called the- La Chateliers principal

88
Q

Why can’t titrations be done on large scale industry

A

Volumes of solutions are too large for titration method

Large volumes of liquid need to be heated and crystallised

89
Q

Why does the voltage of the cell decrease when the cell is left connected in circuit

A

Reactants are being used up

90
Q

What factors should we be considering when choosing final pathway on how to make a product

A

Usefulness of by product, atom economy, cost of energy, yield of product and rates of reaction

91
Q

How to do gold calculations

A

Carat given \ 24

92
Q

What effect does Higher temperature have on equilibrium

A

Higher temperatures reach equilibrium faster because molecules move faster and therefore more frequent collisions because more molecules have energy. More molecules have required energy therefore yield will be lower because higher temperatures favour the endothermic reaction and so equilibrium shifts to the left hand side

93
Q

What should model of crystal look like

A

3D

Particles of different sizes

94
Q

Why does magnesium oxide have such a high temperature

A

Magnesium has very strong bonds so requires a lot of energy to separate magnesium and oxygen ions to melt solid

95
Q

Compare strong and week acids

A

Strong acid is completely ionised in solution whereas weak acid is only partly ionised

96
Q

Describe exothermic reactions

A

One which gives out energy to the surroundings, usually in the form of heat and usually shown by a rise in temperature of the surroundings

97
Q

Describe endothermic reactions

A

One which takes in energy from the surroundings, usually in the form of heat and usually shown by a fall in temperature of the surroundings

98
Q

Give example of nano particle

A

Fullerenes include nanotubes, tiny hollow carbon tubes. All those covalent bonds make nano particles very strong

99
Q

As particle size decreases what happens to the nano particle

A

Size of surface area increases in relation to their volume- surface area to volume ration increases

100
Q

What can nano parcels be used for

A

Catalysts, suncreams, deodorants

101
Q

Can nano particles conducts electricity

A

Yes

102
Q

What can silver nano particles be used for

A

Added to polymer fibres, used to make surgical masks and wound dressings. Gives fibres antibacterial properties

103
Q

Nano particles can

A

Be added to plastics to make them stronger and more durable without adding much mass

104
Q

How does nano medicine work

A

Tiny fullerenes are absorbed more easily by the body than most particles. This means they could deliver drugs right into the cells where they’re needed

105
Q

What happens at the cathode in electrolysis of aqueous solutions

A

If H+ ions and metal ions are present, hydrogen gas will be produced if the metal is more reactive than hydrogen.
If the metal is less reactive than hydrogen, then a solid layer of the pure metal will be produced instead.

106
Q

What happens at the anode in the electrolysis of aqueous solutions

A

At the anode, if halide ions are present- chlorine, bromine and iodine, molecules of them will be formed. If NO halide ions are present then oxygen will be formed from the hydroxide ions

107
Q

What is electrolysis of aqueous solutions

A

As well as ions from ionic compound, there will be H+ ions and OH- ions

108
Q

What happens to positive metals in electrolysis

A

Reduced at the cathode

109
Q

What happens to negative ions in electrolysis

A

Oxidised at anode

110
Q

How to set up an electrochemical cell

A

Get two electrodes (should be inert eg- platinum or carbon). Clean the surfaces of the electrodes using a piece of sandpaper. Don’t touch the metals again otherwise you could transfer grease. Place both electrodes in a beaker filled with your electrolyte, connect the electrodes to a power supply using crocodile clips and wires.

111
Q

Explain how to set up non intert electrodes in electrolysis

A

Eg- copper electrodes in solution of copper sulfates. Follow same method but use non inert electrodes. As reaction continues, the mass of the anode will decrease and the mass of the cathode will increase. This is because copper is transferred from the anode to the cathode.
Leave cell running for 30 mins to get a decent change in mass

112
Q

What metals are more and less reactive than hydrogen

A

Less- copper, silver, gold and platinum

113
Q

What’s bioleaching- a and d

A

Uses bacteria to grow on a low grade ore. The Bacteria produce a solution containing copper ions called leachate. Copper is extracted from the leachate by displacement using scrap iron, then purified by electrolysis.
A-doesn’t require high temperatures
D- toxic substances and sulfuric acid can be produced by the process, and damage the environment

114
Q

What’s phytomining- a and d

A

Involves growing plants that absorb metal compounds. The plants are burned to form ash, from which the metal is extracted.
A- can extract metals from contaminated soils
D- more expensive than mining some ores, growing plants is dependent on weather conditions

115
Q

What are native Elements found

A

Found un combined and unstable - silver and gold

116
Q

How to extract zinc, iron and copper

A

Heat / extract with carbon

117
Q

How to extract potassium, sodium, calcium, magnesium and aluminium

A

Electrolysis of a moleton compound- stable (because they are more reactive)

118
Q

Advantages to both bioleaching and phytoextraction

A

No harmful gases e.g. - sulfur dioxide is produced
Causes less damage to the landscape than mining
Conserves supplies of higher grade ores

119
Q

What happens if u increase temperature

A

The equilibrium will move in the endothermic direction to absorb the extra heat

120
Q

What happens if u decrease the temperature

A

The equilibrium will move in the exothermic direction to produce more heat

121
Q

What does change in pressure only effect

A

Changing pressure only effects equilibrium involving gases

122
Q

What happens if you increase the pressure

A

The equilibrium will move towards the side that has fewer moles of gas to reduce pressure

123
Q

What happens if you decrease the pressure

A

The equilibrium will move towards the side that has more moles of gas to increase the pressure

124
Q

What happens if you increase concentration of REACTANTS

A

The equilibrium will move to the right to use up the reactants (making more products)

125
Q

What happens if you increase the concentration of the PRODUCTS

A

the equilibrium will move to the left to use up the products (making more reactants)

126
Q

What happens if you decrease the concentrations

A

It will have the opposite effect

Chemistry revision (10 decks)

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