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Chemistry > Unit 3a - Elements, Water And Organic Chemistry > Flashcards

Unit 3a - Elements, Water And Organic Chemistry Flashcards

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1
Q

Until quite recently what was the two obvious ways to categorise elements?

A

Their physical and chemical properties and their relative atomic mass

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2
Q

before 1800 what could scientists go on to classify elements?

A

In order of atomic mass

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3
Q

Before the 20th century why did elements not have an atomic number?

A

Scientists had no idea of atomic structure or of protons and electrons so there was no such thing as an atomic number

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4
Q

Where did the name periodic table come from?

A

A periodic pattern was noticed in the properties of the ordered elements

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5
Q

In 1864 who tried arranging the periodic table more usefully?

A

Newlands

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6
Q

What year did newland try to arrange the elements more usefully?

A

1864

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7
Q

What did newlands notice about the elements?

A

That every eighth element had similar properties

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8
Q

What was newlands sets of eight called?

A

Newlands octaves

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9
Q

Why did newlands pattern break down on the third row?

A

Because transition metals like titanium (Ti) and Iron (Fe) messed it up

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10
Q

Why was newlands work ignored?

A

Because he left no gaps (but he was getting pretty close)

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11
Q

When newland presented his ideas to the chemical society in 1865 why was his work critiqued? (3)

A
  1. His groups contained elements that didn’t have similar properties e.g carbon and titanium
  2. He mixed up metals and non-metals e.g oxygen and iron
  3. He didn’t leave any gaps for undiscovered elements
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12
Q

How did newlands set out his periodic table?

A

He listed some of the known elements in rows of seven and every column should of had elements with similar properties. Because if it was all put out in list form every eighth element would have similar properties.

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13
Q

When did dmitri mendeleev arrange the elements into a table of elements?

A

1869

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14
Q

What was mendeleevs idea for how to set out the periodic table?

A

He put the elements in order of atomic mass but left gals in order to keep elements with similar properties in the same vertical columns (groups). These gaps helped predict the properties of undiscovered elements and when they were found and they fit the pattern it was good for mendeleev. He left very big gaps in the first two rows before the transition metals come in on the third row.

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15
Q

Why did the big break through for the periodic table happen?

A

Because the structure of an atom was understood better

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16
Q

Why didn’t all scientists think the periodic table was important?

A

They thought it was a bit of fun because there wasn’t much evidence to suggest the elements really fit together and ideas don’t get the scientific approval without evidence.

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17
Q

After Mendeleev released his work what convincing evidence did they find in favour of the periodic table?

A

Newly discovered elements fitted into the gaps he left

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18
Q

When did scientists discover protons, neutrons and electrons?

A

The late 19th century

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19
Q

Why do scientists now accept the periodic table as being a very important and useful summary of the structure of atoms?

A

Because it matches up very well to what’s been discovered about the structure of atoms.

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20
Q

What is the modern periodic table based on?

A

Electronic structure

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21
Q

What happened to the periodic tables arrangement when electrons, protons and neutrons were discovered?

A

The elements were arranged in order of atomic number instead of atomic mass

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22
Q

In the modern periodic table what we’re all the elements put into?

A

Groups

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23
Q

In the modern periodic table how can you predict the elements chemical properties?

A

(Because the periodic table is arranged by electronic structure) you can use the electron arrangement to predict their chemical properties

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24
Q

How are electrons in an atom set out?

A

In shells which each correspond to an energy level

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25
Q

(Apart from transition metals) what do elements in the same group have in common?

A

The same number of electrons in their highest occupied energy level (outer shell)

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26
Q

What are the group numbers in the modern periodic table equal to?

A

The number of electrons in the outer shell e.g group six have six electrons in their outer shell.

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27
Q

What does the positive charge of the nucleus do?

A

Attracts electrons and holds them in place

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28
Q

If an electron is far from the nucleus ,compared to if it was closer, what happens to the attraction?

A

There is less attraction

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29
Q

What happens to the attraction when there is a lot of inner electrons? And why?

A

It is even less because the inner electrons get in the way of the nucleur charge and this reduces the attraction - this is known as shielding

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30
Q

What does the combination of increased distance from the nucleus and increased shielding mean? (2)

A

That an electron in a higher energy level is more easily lost because there’s less attraction from the nucleus holding it in place this is why group 1 metals get more reactive as you go down the group.
It also means that a higher energy level is less likely to gain an electron as there’s less attraction from the nucleus pulling electrons into the atom that’s why group 7 elements get less reactive going down the group.

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31
Q

What are alkali metals?

A

Silvery solids that have to be stored in oil and handled with forceps as they burn the skin

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32
Q

As you go down in group one what do the alkali metals do? (2)

A

Become more reactive because the outer electron is more easily lost as its further from the nucleus and have lower melting and boiling points

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33
Q

What kind of density do the alkali metals have?

A

Low. The first three in the group are less dense than water.

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34
Q

What are the alkali metals? (6 - know first three v well)

A 
Lithium*
Sodium*
Potassium*
Rubidium
Caesium
Francium
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35
Q

Why are the alkali metals a all very reactive with similar properties?

A

They all have one outer electron

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36
Q

When an alkali metal is reacted with a non metal what does it form?

A

An Ionic compound

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37
Q

What must the alkali metal react with to form an ionic compound?

A

A non-metal

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38
Q

Why do alkali metals and non-metals form ionic compounds?

A

Because the alkali metals are eager to lose their outer electron to form a 1+ ion. They never form covalent bonding as they just want to lose the outer electron so they wouldn’t share. So they always form ionic bonds.

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39
Q

What do ionic compounds produce?

A

White compounds that dissolve in water to form colourless solutions

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40
Q

When alkali metals are reacted with water what does it produce?

A

Hydrogen gas

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41
Q

In general, What happens when lithium, sodium or potassium are put in water?

A

They react vigorously, they float and move around the surface fizzing furiously and they produce hydrogen. They form hydroxides that dissolve in water to give alkaline solutions

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42
Q

When potassium reacts with water what happens?

A

It moves around the surface producing hydrogen and it gets so hot it ignites the hydrogen

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43
Q

How would you show that hydrogen is produced when reacting an alkali metal in water?

A

A lighted splint will indicate hydrogen by producing a squeaky pop as the hydrogen ignites

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44
Q

When the alkali metal has reacted fully with the water what colour would the universal indicator change to?

A

Purple as the mixture has now become alkaline

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45
Q

What is the equation to react sodium (Na) in water?

A

2Na + 2H 0 —-> 2NaOH + H
2 2

This is the same format for all the alkali metals

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46
Q

What is the name for group 7 of the periodic table?

A

The halogens

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47
Q

As you go down group 7 what are the properties of the halogens?

A

They are less reactive because it’s harder to gain an extra electron, because the outer shells further from the nucleus. Has a higher melting and boiling point

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48
Q

What are the halogens?

A

Non-metal molecules with coloured vapours

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49
Q

What are the properties of fluorine?

A

Very reactive poisonous yellow gas

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50
Q

What are the properties of chlorine?

A

Fairly reactive poisonous dense green gas

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51
Q

What are the properties of bromine?

A

A dense poisonous red-brown volatile liquid

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52
Q

What are the properties of iodine?

A

A dark grey crystalline solid or a purple vapour

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53
Q

What is a molecule?

A

A pair of atoms

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54
Q

List the halogens

A 
Fluorine 
Chlorine
Bromine
Iodine 
Astatine
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55
Q

What kind of bond do the halogens form with metals?

A

Ionic bond

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56
Q

What do the halogens form in ionic bonding?

A

1- ions called halides e.g Na+Cl-

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57
Q

Explain ionic Bonding

A

When a metal reacts with a non metal e.g is because the sodium (metal) gave up an electron so it could have a full outer shell therefore meaning it has more protons so it’s a positive charge so it’s a plus and the chlorine (non metal) gained an electron to have a full outer shell so it has more electrons making it a negative charge so it’s a minus

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58
Q

What happens if a more reactive halogen is reacted with a less reactive halogen from an aqueous solution of its salt?

A

The more reactive one with displace the less reactive one e.g chlorine can displace bromine and iodine from an aqueous solution of its salt and bromine can also displace iodine because of the trend in reactivity.

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59
Q

Where are transition elements located?

A

They make up the big clump of metals in the middle of the periodic Table

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60
Q

What are the Properties of the transition metals (4)?

A
  1. Good conductors of heat and electricity
  2. Very dense, strong and shiny
  3. They are less reactive than group 1 metals - they don’t react as vigorously with water or oxygen
  4. They are much denser, stronger and harder than the group 1 metals and have a higher melting point (except Mercury as that’s a liquid at room temp) e.g iron melts at 1500c, copper at 1100c
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61
Q

What do transition metals often have?

A

More than one ion e.g iron Fe2+ and Fe3+, copper Cu+ and Cu2+ and chromium Cr2+ and Cr3+

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62
Q

What do the different ions usually form?

A

Different coloured compounds e.g Fe2+ usually gives green compounds whereas Fe3+ usually forms red/brown ones - like rust

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63
Q

Why are compounds colourful?

A

Because of the transition metal ion they contain

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64
Q

What colour is the compound potassium chromate (VI)?

A

Yellow

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65
Q

What colour is the compound potassium manganite (VI)?

A

Purple

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66
Q

What colour is the compound copper(II) sulfate?

A

Blue

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67
Q

What are the colours in gemstones like blue sapphires and green emeralds and the colours in pottery glazes due to?

A

Transition metals

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68
Q

What colour is weathered copper?

A

Green

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69
Q

Do transition metals and their compounds make good catalysts?

A

Yes

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70
Q

What catalyst is used in the haber process to make ammonia?

A

Iron

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71
Q

What catalyst is used for the decomposition of hydrogen peroxide?

A

Manganese(IV) oxide

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72
Q

What catalyst is used for turning oils into fats for making margarine?

A

Nickel

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73
Q

What do you need to know about transition metals?

A

They form ions with different charges, form coloured compounds and make good catalysts

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74
Q

What does whether water is hard or soft depend on?

A

The rocks the water meets on the way

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75
Q

What does hard water make?

A

Scum and scale

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76
Q

When adding soap to soft water what do you get?

A

A Lather

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77
Q

When adding soap to hard water what do you get?

A

A nasty scum (unless you’re using a soapless detergent)

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78
Q

Why does hard water create scum when soap is added?

A

Dissolved calcium ions and magnesium ions in the water reacts with the soap to create scum

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79
Q

Why is hard water a waste of money?

A

Because to get a decent lather you need more soap but soap isn’t free so that means more money is used buying soap than if you had soft water

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80
Q

When heated, what does hard water form on the inside of pipes, boilers and kettles?

A

Scale (mostly Calcium carbonate)

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81
Q

Where does scale usually reside?

A

On the insides of pipes, boilers and kettles

82
Q

Why is having badly scaled up pipes and boilers bad? (2)

A

Because it reduces efficiency of heating systems cause scale is a thermal insulator so a kettle with scale on the heating element takes longer to boil than a clean kettle so it’s less efficient
and it may need to be replaced which costs money as scale can eventually block pipes

83
Q

What is hardness of water caused by?

A

Ca2+ and Mg2+ ions

Calcium and magnesium ions

84
Q

What does water go through to make it become hard?

A

As rain falls on some types of rocks e.g limestone, chalk and gypsum, it can dissolve compounds like magnesium sulfate (which is soluble) and calcium sulfate (which is slightly soluble)

85
Q

What are calcium ions goods for?

A

Healthy teeth and bones

86
Q

What are the benefits of hard water? (2)

A

Some say people who live in hard water areas are at less of a risk of developing heart disease than people who live in soft water areas due to the minerals in hard water .
Calcium is good for teeth and bones.

87
Q

What are the two kinds of hard water?

A

Temporary and permanent

88
Q

What is temporary hardness caused by?

A

Hydrogencarbonate ion, HC0 - in Ca(HC0 )

3 3 2

89
Q

What causing permanent hardness?

A

Dissolved calcium sulfate

90
Q

How do you remove temporary hardness?

A

By boiling. When heated the Cali um Hydrogencarbonate decomposes to form calcium carbonate which is insoluble. This solid is the lime scale on your kettle.

91
Q

What is the word equation for removing temporary hardness?

A

Calcium Hydrogencarbonate —> calcium carbonate + water + carbondioxide

92
Q

Why doesn’t boiling remove permanent hardness?

A

Heating a sulfate doesn’t do anything

93
Q

What is the method to soften both types of hard water using washing soap?

A

Add washing soda (sodium carbonate Na CO ) to it.
2 3
The added carbonate ions react duty the Calcium and magnesium ions to make an insoluble precipitate of calcium carbonate and magnesium carbonate. The calcium and magnesium ions are no longer dissolved in the water so they can’t make it hard.

94
Q

What is the equation for softening water using washing soap?

A

Ca2+ CO 2- —> CaCO

3 3

95
Q

What is another way to remove hardness from water using an exchange?

A

By running water through an ion exchange column as the columns have a lot of sodium or hydrogen ions and exchange them for calcium or magnesium ions running in the water softening the water.

96
Q

What is the equation for softening water using the ion exchange column?

A

Na Resin + Ca2+ —> CaResin + 2Na+

2

97
Q

Explain how you could use a titration to compare the hardness of water samples? (8)

A
  1. Fill a burette with 50cm3 of soap solution
  2. Add 50cm3 of the first sample into a flask
  3. Use the burette to add 1cm3 of soap solution to the flask
  4. Put a bung in the flask and shake for 10seconds
  5. Repeat steps three and four until a good lasting lather is formed
  6. Record how much soap was needed go create a lasting lather
  7. Repeat the steps with the other water samples
  8. Next, boil fresh samples of each type of water for ten minutes and repeat the experiment
98
Q

What is a lasting lather?

A

Where the bubbles cover the surface for at least thirty seconds

99
Q

As water is essential for life what must it be free from? (2)

A

Poisonous salts e.g phosphates and nitrates

Harmful microbes as they can cause diseases such as cholera and dysentery

100
Q

Where does most of our drinking water come from?

A

Reservoirs

101
Q

How does water get into reservoirs?

A

By flowing in from rivers and groundwater and company’s choose to build reservoirs when there’s a good supply of water

102
Q

Where do government agencies keep a close eye on for pollution?

A

Reservoirs, rivers and groundwater

103
Q

The water treatment stages the water from reservoirs goes through (4)

A
  1. Water is passed through a mesh screen to remove big bits like twigs (screening)
  2. Chemicals are added to make solids and microbes stick together and fall to the bottom (removal of solids)
  3. The water is filtered through gravel beds to remove all the solids (filtration)
  4. Water is chlorinated to kill off any harmful microbes left (chlorination)
104
Q

What do the filters people buy to filter tap water in their homes contain?

A

Carbon or silver

105
Q

What do the carbon and silver in the home filters do?

A

Carbon removes chlorine taste and silver is supposed to kill germs

106
Q

What do some people in hard water areas buy?

A

Water softener which contain ion exchange resins

107
Q

How do you produce totally pure water with nothing dissolved in it?

A

By distillation - boiling water to make steam and condensing the steam.

108
Q

Why can’t we use distillation to produce tap water?

A

It is too expensive and requires a lot of energy to boil all the water we use

109
Q

Where is distilled water used and why?

A

In chemistry laps so in an experiment there is nothing in the water like ions that could change the results of an experiment

110
Q

Why is fluoride added to drinking water in some parts of the country?

A

It helps reduce tooth decay

111
Q

Why is chlorine added to water?

A

It prevents diseases

112
Q

What are some drawbacks to adding chlorine to water?

A

It has been linked to an increased risk in certain cancers -
It can react with natural substances in water to product toxic-by- products which some say could cause cancer

113
Q

What are some drawbacks to adding fluoride to water? (2)

A

In high doses it can cause cancer and bond problems in humans so some believe it shouldn’t be added to water.
People also have the concern if it’s right to “mass medicate” cause people can choose to use fluoride toothpaste but they can’t choose whether there water has fluoride in.

114
Q

Why does the level of chemicals added to drinking water need to be monitored?

A

In some areas the water may already contain a lot of fluoride so adding more may be harmful etc.

115
Q

What is a reversible reaction?

A

The proud to of the reaction can themselves react to product the original reactants

116
Q

What is the symbol for a reversible reaction?

A

______\
______
\

117
Q

If a reversible reaction takes place in a closed system what will always be reached?

A

A state of equilibrium

118
Q

What does a state of equilibrium mean?

A

The amount of reactants and products will reach a certain balance.
The reactions are still taking place in both directions but there is no overall effect because the forward and backwards reactions cancel each other out. The reactions are taking place at exactly the same rate in both directions.

119
Q

What is a closed system?

A

A place where none of the reactants or products can escape

120
Q

What are the two things that the position of equilibrium depend strongly on?

A

The temperature and pressure surrounding the reaction

121
Q

What would happen if you altered the temperature and pressure of a reversible reaction?

A

The position of equilibrium would move to give more product and less reactants

122
Q

Explain how temperature can change the position of the equilibrium in a reversible reaction

A

All reactions are exothermic in one direction and endothermic in the other

If you raise the temperature the endothermic reaction will increase to use up the extra heat but if you reduce the temperature the exothermic reaction will increase to give out more heat

Increase heat the equilibrium seeks to lower the temperature so favours endothermic reaction
Decrease heat the equilibrium weeks go increase the temperature and favours exothermic reaction

123
Q

Explain how pressure on a reversible reaction can change the position of the equilibrium

A

Many reactions have a greater volume on one side, either of products or reactants (but if it’s the same then changing pressure doesn’t help)

If you raise the pressure it will encourage the reaction which produces less volume
If you lower the pressure it will encourage the reaction which produces more volume

124
Q

Why does adding a catalyst not change the equilibrium position?

A

Catalyst speed up both the forward and backward reactions by the same amount so adding a catalyst means the reaction reaches equilibrium quicker but you end up with the same amount of product as you would without the catalyst

125
Q

What does the Haber process produce?

A

Ammonia (NH ) which is used to make fertilisers

3

126
Q

What elements are needed to make ammonia?

A

Nitrogen and hydrogen

127
Q

What is the chemical equation to make ammonia?

A

N + 3H reversible symbol 2NH (+ heat)

2 2 3

128
Q

Where is the nitrogen obtained from in the Haber process?

A

From the air which is about 78% nitrogen and 21% oxygen

129
Q

Where does the hydrogen needed in the Haber process come from?

A

Natural gas or from other sources like crude oil

130
Q

What kind of reaction is the Haber process?

A

It is reversible so the nitrogen and hydrogen react to form ammonia and this can break down again into nitrogen and hydrogen

131
Q

Can the Haber process reach an equilibrium?

A

Yes

132
Q

For the Haber Process what are the best industrial conditions?

A

Pressure at 200 atmosphere , temperature at 450*C and an iron catalyst

133
Q

Explain why in the Haber process the pressure is at 200 atmosphere

A

Because higher pressure favours the forwards reaction since there are four molecules of gas on the left hand side for every two on the right
So the pressure is set as high as possible to give the best percentage yield without making the plant too expensive to build as having a pressure of 1000 would be very expensive so it is at 200 instead

134
Q

Explain why in the Haber process the temperature is set at 450*c

A

The forward reaction is exothermic which means that increasing the temperature will actually move the equilibrium the wrong way toward the nitrogen and hydrogen and the yield for ammonia would be best at a lower temperature.
However lower temps means a lower rate of reaction so they increase the temperature anyway to get a faster rate of reaction.
The 450*c is a compromise between the maximum yield and speed of reaction as its bet to wait 20 seconds for 10% yield than 60 seconds for 20% yield.

135
Q

What happens to the ammonia in the Haber Process?

A

As it is formed it is a gas but it cools in a condensed so it liquefies and is removed to be used

136
Q

What happens to the used hydrogen and nitrogen in the Haber process?

A

They are recycled so nothing is wasted

137
Q

What does the iron catalyst in the Haber process do?

A

It makes the reaction go faster which gets it to the equilibrium proportions more quickly but it does not affect the position of equilibrium (I.e the % of yield obtained)

138
Q

Why is the iron catalyst in the Haber process so important?

A

Without it the temperature would have to be raised even further to get a quick enough reaction and that would rescue the % yield even further so the catalyst is important

139
Q

Why is the temperature in the Haber process so high when it would benefit from a lower temperature?

A

It is not high for a better equilibrium but for speed and it doesn’t matter the percentage yield is low because the unused hydrogen and nitrogen is recycled

140
Q

How the Haber process works

A

Hydrogen and nitrogen are put into the machine in the ratio 3:1 , they travel to the reaction vessel which has trays of the iron catalyst in to speed up the reaction, the reaction vessel is at 450*c and 200 atmosphere and this creates ammonia gas. The gas is cooked in the condenser and the unused H2 and N2 are recycled back into the plant.

141
Q

What is the functional group of alcohols?

A

-OH

142
Q

What do alcohols end in?

A

-ol

143
Q

What is the general formula for an alcohol?

A

C H OH

n 2n+1

144
Q

What is the formula of an alcohol with two carbons?

A

C H OH

2 5

145
Q

What are the first three alcohols in the homologous series and what’s a good way to remember them

A

Methanol, Ethanol, propanol

My elephant peels

146
Q

What is the structure and formula of methanol

A 
H
      |
H-C-O-H
      |
     H

CH OH
3

147
Q

What is the structure and formula for ethanol

A 
H   H
      |    |
H-C-C-O-H 
      |   |
     H  H

C H OH
2 5

148
Q

What is the structure and formula for propanol

A 
H   H H
      |    |   |
H-C-C-C-O-H
      |   |    |
     H  H  H

C H OH
3 7

149
Q

What is the basic naming system for alcohols?

A

It is the same as the Alkane but replace the final -e with -ol e.g butane would be butanol

150
Q

Why cant you write CH O instead of CH OH

4 3

A

Because it doesn’t show the functional -OH group

151
Q

What are the properties of the first three alcohols? (3)

A
  1. They are flammable , they burn in air to produce carbon dioxide and water
  2. They all dissolve completely in water to form neutral solutions
  3. They react with sodium to give hydrogen and alkoxides e.g ethanol gives sodium ethoxide and Hydrogen
152
Q

What is the main alcohol used in alcoholic drinks? And why?

A

Ethanol because it’s not as toxic as methanol as that causes blindness if drunk

153
Q

What is a drawback to drinking ethanol?

A

It damages the liver and brain

154
Q

Why can alcohols like methanol and ethanol be used as solvents?

A

Because they can dissolve most compounds that water dissolves but that can also dissolve substances that water can’t dissolve like oils and fats

155
Q

What are some substances that alcohols can dissolve but water can’t? (3)

A

Hydrocarbons, oils and fats

156
Q

What is ethanol a solvent for and why?

A

Perfumes and aftershave lotions because it can mix with both the oils (which give the smell) and the water (that makes up the bulk of it)

157
Q

What is methylated spirit?

A

Ethanol with chemicals like methanol added to it

158
Q

What is methylated spirit used for?

A

To clean point brushes and as a fuel

159
Q

Why is purply-blue dye added to methylated spirit?

A

It is poisonous to drink so the colour stops people drinking it by accident

160
Q

How can ethanol be used as a fuel? (3)

A
  • ethanol is used as a fuel in spirit burners as it burns fairly cleanly and doesn’t smell
  • ethanol can be mixed with petrol and used as a fuel for cars because pure ethanol is clean burning so the more ethanol in the petrol the less pollution
  • some countries have little oil deposits but lots of land like Brazil so they grow loads of sugar cane which ferments to form ethanol and sugar cane is a renewable resource which is an advantage
161
Q

What is the equation for burning alcohol for example methanol in the air?

A

2CH OH + 3O —> 2CO + 4H O

3 2

162
Q

What is the equation for reaction sodium and an alcohol for example ethanol?

A

2C H OH + 2Na —> 2C H ONa + H

2 5 2 5 2

163
Q

What is the functional group of carboxylic acids?

A

-COOH

164
Q

How would you recognise a carboxylic acid from a name?

A

Their names end in -anoxic acid and start with the normal (meth/eth/prop) etc.

165
Q

What is the structure of methanoic acid and its formula?

A 
O
      //
H-C
       \
        OH

HCOOH

166
Q

What is the structure and formula of ethanoic acid?

A 
H    O
      |    //
H-C-C
      |     \
      H    OH

CH COOH
3

167
Q

What is the structure and formula of propanoic acid?

A 
H   H     O
      |     |     //
H-C- C-C
      |     |      \
      H   H      OH

C H COOH
2 5

168
Q

When carboxylic acid reacts with carbonates what is produced?

A

Salt, water and carbondioxide

169
Q

What do the salt form when carboxylic acid and carbonates react end in?

A
  • anoate for example methanoic acid will form a methanoate
170
Q

Give the word equation for if ethanoic acid and sodium carbonate reacted

A

Ethanoic acid + sodium carbonate –> sodium ethanoate + water + carbon dioxide

171
Q

When carboxylic acids dissolve in water what does it produce?

A

Acidic solutions

172
Q

What happens when a carboxylic acid dissolves in water?

A

They ionise and release H+ ions which are responsible for making the solution acidic but because they don’t ionise completely (not many H+ ions are released) they form weak acidic solutions so they have a higher PH that aqueous solutions of strong acids with the same concentration

173
Q

How is the strength of an acid different to the concentration?

A

Concentration is how watered down your acid is and strength is how well it has ionised in the water

174
Q

How can you make ethanoic acid?

A

By oxidising ethanol. Microbes like yeast cause the ethanol to ferment and ethanol can also be oxidised using oxidising agents.

175
Q

Give the word equation for making ethanoic acid

A

Ethanol + oxygen –> ethanoic acid + water

176
Q

How can you make vinegar?

A

Oxidising ethanol to create ethanoic acid which can be dissolved in water to make vinegar

177
Q

Uses of vinegar (2)

A

Flavouring and preserving food

178
Q

Where is citric acid present?

A

Oranges and lemons and manufactured to make fizzy drinks

179
Q

What is a good use of citric acid?

A

To get rid of scale

180
Q

What can carboxylic acids with longer chains of carbon atoms be used for in the industry?

A

To make soap and detergents

181
Q

What can carboxylic acids be used in the preparation of?

A

Esters

182
Q

Ethanoic acid is a good solvent for many organic molecules, but why isn’t it usually chosen as a solvent?

A

Because it makes the solution acidic

183
Q

What is the functional group of an ester?

A

-COO-

184
Q

How are esters formed?

A

From an alcohol and a carboxylic acid and an acid catalyst is usually used e.g concentrated sulfuric acid

185
Q

Give the general word equation for making an ester

A

Alcohol + carboxylic acid –> ester + water

186
Q

Give the structural equation to make an ester from ethanoic acid and ethanol

A

H O. H. H. H. O. H
| //. |. |. |. //. /
H-C-C + HO-C-C-H —> H-C-C. H H. + O
| . |. |. |. . |. |. \
H OH. H. H. H. O-C-C-H. H
|. |
H. H
Ethanoic acid Ethanol Ethyl ethanoate water
CH COOH. C H OH. CH COOC H H O
3. 2. 5 3. 2. 5. 2

187
Q

How do you figure out the name of the ester?

A

The alcohol for,s the first part of the name(then it’s - Yl on the end) and the acid forms the second part ( and -oate on the end)
E.g ethanol + ethanoic acid –> ethyl ethanoate + water

188
Q

What do esters usually smell like?

A

Quite sweet and fruity and pleasant

189
Q

Esters are quite v____

A

Volatile

190
Q

Why does esters volatility make them ideal for perfumes?

A

The evaporated molecules can be detected by smell receptors in your nose

191
Q

Why does esters volatility make them potentially dangerous?

A

Because many esters are flammable

192
Q

Why don’t esters mix well with?

A

Water (they are no where near as soluble as alcohols or carboxylic acids)

193
Q

What do esters mix well with? (2)

A

Alcohols and organic solvents

194
Q

Why are esters used in perfumes?

A

Because they smell nice

195
Q

What, besides perfumes, are esters used to make? (4)

A

Flavourings, aromas, ointments (deep heat), solvents (for paint glue and nail varnish)

196
Q

Why are esters used to make flavourings and aromas?

A

Because there are some esters that smell or taste of rum, Apple , orange , banana , grape, pineapple etc

197
Q

What makes an ester dangerous? (3)

A
  1. Inhaling the fumes of some esters can irritate mucous membrane in the nose and mouth
  2. Ester fumes are heavier than air and flammable - flammable vapour + naked flake = flash fire
  3. Some esters are toxic especially in large doses so some people worry about health problems associated with synthetic food additives like esters
198
Q

Why are esters a better solution that some other organic solvents?

A

Because they aren’t as volatile of as toxic as some and they don’t release nearly as many toxic fumes as some of the organ solvents - esters have even replaced solvents such as toluene in many paints and varnishes

199
Q

Examples of esters and their smells

A

Methyl butanoate - pineapple, Apple
Methyl pentanoate- flowery
Octyl butanoate - parsnip
Octyl ethanoate - orange

200
Q

What is washing soap?

A

Sodium carbonate

Chemistry (6 decks)

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