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Chemistry P2 *fun* Flashcards

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1
Q

1) What is a compound?

2) Why is it difficult to break a compound?

A

A substance containing at least two elements that have been chemically bonded

Because of the electrostatic forces between the elements particles

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2
Q

1) What is an isotope?

2) Why do isotopes have the same atomic numbers but different mass numbers?

A

1) An isotope is a different atomic form of the same element.
2) They have different number of neutrons.

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3
Q

Why do atoms react?

A

Atoms want full shells (like the noble gases)

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4
Q

1) If a atom loses an electron what does it become?

2) If a atom gains an electron what does it become?

A

1) A positive ion (group 1 & 2 need to lose electrons for full outer shells)

2) A negative ion
(group 6 & 7 need electrons for full outer shells)

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5
Q

Name the three different types of bonding and which types of elements they occur between?

A

Metallic - a metal and a metal
Covalent - a non-metal and a non-metal
Ionic - a metal and a non-metal

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6
Q

What happens in ionic bonding?

A

Atoms lose/gain electrons to form charged particles (ions), which are then strongly attracted to one another (positive attracts negative)

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7
Q

Name 5 features of ionic compounds

A

1) Strong electrostatic attraction between ions
2) High melting and boiling point (strong forces)
3) When melted, they carry electrical currents - ions separate and are free to move in the solution
4) They dissolve easily
5) Regular lattice structure (forces between ions)

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8
Q

Ionic compounds are made up of a … part and a … part…

The total charge is always 0

A

Ionic compounds are made up of positively charged part and a negatively charged part. The total charge is always 0

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9
Q

How do you draw an ionic bonding diagram?

A

The atomic configurations inside brackets with a positive or negative outside to show how many electrons have been lost/gained

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10
Q

What is covalent bonding?

A

When a compound is formed through two atoms sharing electrons to BOTH obtain full shells.

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11
Q

Name four examples of examples of elements that form simple molecular covalent bonds…

A 
H2 - Hydrogen
Cl2 - Chlorine 	
CH4  -  Methane 	
HCl – Hydrogen Chloride 
NH3 - Ammonia 	
H2O - Water 	
O2- Oxygen
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12
Q

Name the properties of simple molecular covalent bonds…

A

1) Weak intermolecular forces
2) Low melting and boiling points
3) Most are gases or liquids are room temperature
4) They don’t conduct electricity (No ions available to act as current carriers)

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13
Q

How do you draw a Covalent bond diagram?

A

The atomic configurations will overlap with showing their shared electrons as either dots or crosses.

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14
Q

Name three giant covalent bonds…

A

Diamond, Graphite and Silicon Dioxide

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15
Q

Name the properties of diamond…

A

Diamond forms four covalent bonds in a very rigid structure which makes it hard

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16
Q

Name the 3 properties of Graphite…

A

1) Graphite forms three covalent bonds
2) Layers slide over each other bc. it has weak inter molecular forces between the layers
3) Good conductor of heat and electricity (only non-metal) bc. every carbon atom has a delocalised electron (free) that conduct electricity and heat

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17
Q

What is Silicon Dioxide made of?

A

Silicon and Oxygen molecules, is what sand is made of.

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18
Q

What is the difference between covalent lattices and ionic lattices?

A

Covalent lattices have no ions

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19
Q

Name 4 generic properties of Giant Covalent bonds

A

1) High melting/boiling point
2) Don’t conduct electricity even when molten (Except graphite)
3) Strong covalent bonds
4) Insoluable

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20
Q

What are metallic bonds?

A

The strong forces of electrostatic attraction between the positive metal ions delocalised electrons, which hold the atoms together in a regular structure.

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21
Q

Name 3 properties of Giant Metallic bonds

A

1) Neat lattice
2) Malleable
3) Conduct heat and electricity

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22
Q

Explain how delocalised electrons conduct electricity.

A

They come from the outer shell of the metal atoms and are free to move and carry heat/electricity

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23
Q

How do you draw metallic bonding?

A

Rows of neat positive metal ions with random electrons between.

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24
Q

1) What is a alloy

2) Why is an alloy hard?

A

1) A compound of two different metal elements
2) Alloys are hard because they contain different metals atoms of different sizes which distorts the regular arrangement.

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25
Q

Define a smart material.

A

Smart materials behave differently depending on the conditions they are in

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26
Q

What is Nitinol, how does it work and what is it used for?

A

Nitinol is a shape memory alloy, it is half nickel and half titanium.
When heated Nitinol returns to its original ‘set’ shape, it is used for braces (pulling teeth into position) and in glasses (un-squash)

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27
Q

What is a nanoparticles?

What are fullerenes?

A

Nano particles are tiny particles; 1-100 nanometres wide which include fuellerenes.
Fullerenes are molecules of carbon shaped like hollow balls or closed tubes and arranged in hexagonal rings. They contain different number of carbon atoms.

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28
Q

Why are nanotubes strong?

A

Nanotubes are hollow carbon tubes made of joined fullerenes. They have have lots of covalent bonds so are very strong.

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29
Q

What are uses for nanotubes?

A 
Industrial catalysts; larger surface area:volume ratio,
Strong light building materials, 
Suncream and deodorants,
Water purity sensors,
Electrical Circuits,
Lubricants; ball bearings / gears
Possible; nano medicines
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30
Q

1) What is a thermo-setting plastic?

2) Why won’t they melt?

A

1) A plastic with strong intermolecular forces (crosslinks) between the polymer chains.
2) The crosslinks hold them together in solid, rigid strucutes

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31
Q

Qualities of thermosetting polymers?

A

Solid structures
Won’t melt
Strong, hard and rigid

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32
Q

1) What is the strucure of thermosoftening polymers?

2) Do they melt?

A

1) Individual tangled chains of polymers with no cross links?
2) Yep, the weak molecular forces are easily overcome - you can remelt/re-mould over and over again.

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33
Q

What is the Ar?

A

The relative atomic mass, it is the same as the mass number of the element

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34
Q

What is Mr?

A

A compound has a relative formula mass, which is all the atomic masses added together

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35
Q

What is the equation for a mole?

A

moles= mass (g) /Mr

36
Q

How do you calculate the % mass of an element in a compound?

A

(Ar* number of atoms of THAT element) ÷ Mr of the whole compound
Answer * 100

37
Q

How do you calculate the empirical formula?

A

1) Write down the experimental masses or percentages given
2) Divide each mass/percentage by the Ar for that element
3) Multiply above answer to get a whole number
4) Simplify numbers (imagine they are a ratio)

38
Q

How do you calculate the masses in a reaction?

A

1) Write down the balanced equation
2) Rewrite the equation replacing the words/symbols with the Mr
3) Divide the Mr of the substance you have the information about to get 1
4) Times by the mass you want to calculate

39
Q

How do you calculate the percentage yield?

A

Percentage Yield = actual yield ÷ predicted yield

Answer * 100

40
Q

Why are percentage yields less than 100?

A 
#1 Reversible reactions; some products react together & changing back to original reactants, not all the reactants are converted to products
#2 Filtration; when filtering a liquid to remove solid particles, some of the liquid/solid is lost 
#3 Unexpected reactions; unexpected reactions can occur using up reactants, not as much reactant left to create the product
41
Q

Why is product yield important?

A 
For sustainable development.
#1 Shouldn't use resources faster than they're replaced to conserve them
#2 Using as little energy for the highest yield saves resources
42
Q

How do you use paper chromatography?

A

1) Put spots of the colored solution on a piece of chromotography paper along a pencil baseline
2) Put the sheet into a beaker of solvent ensuring the baseline is above the solvent level
3) As the solvent seeps up the paper the dyes are carried too,

43
Q

What is an instrumental method?

A

A method using machines

44
Q

Name an instrumental method of identifying unknown substances.
How does it work (stages)?

A

Gas chromatography linked to mass spectroscopy (GC-MS)

1) A gas, carries different substances through a column filled with solid material
3) The substances travel through at at different speeds, separating
2) The time taken for a substance to travel through the column is called the retention time and is measured by a detector. This can be used to help identify the substance
3) A recorder draws a gas chromograph
4) The gas chromatography column can be linked to a mass spectrometer (GC-MS) which is used to identify the substances leaving the end of the column

45
Q

1) What information can you read of a gas chromograph?

2) A GC-MS graph?

A

1) The number of compounds (=number of peaks) and the retention time (distance from y axis)
2) The relative molecular mass (Mr) of each of the substances separated in the column (height of molecular ion peak)

46
Q

Why do we use a mass spectrometer?

A

It can detect very small quantities, and identify substances quickly and accurately

47
Q

1) What is the rate of reaction equation?

2) Name 3 ways to measure the rate of reaction?

A

1) Rate of reaction= amount of react used/amount of product formed ÷ time

#1 Mass balance; when gas is released-the mass changes
#2 Volume of gas given off; measure volume of gas produced in a gas syringe
#3 Precipitation; precipitates clouds solution
48
Q

What 4 things affect the rate of reaction?

A

1) Temperature
2) Catalyst
3) Concentrated (or pressure in gases)
4) Surface area

49
Q

1) What is collision theory?

2) When do reactions only happen?

A

1) The rate of a reaction depends on how often and how hard reacting particles collide
2) Reactions only happen if particles collide with enough energy

50
Q

How does temperature affect the rate of reaction?

A

Higher temperature mean particles move faster so collide more and with greater energy-if they collide hard enough they will react

51
Q

How does a higher concentration/pressure affect the rate of reactions?

A

If solution is made more concentrated there are more particles of reactant meaning collisions between important particles are more likely

If theres more pressure the particles are squashed together which increases the frequency of successful collisions and rate of reaction

52
Q

How does a larger surface area affect the rate of reactions?

A

Larger surface area means more area exposed so there are more frequent successful collisions-more area to react with

53
Q

What is a catalyst?

A

A substance that speeds up the rate of a reaction without being changed or used up

54
Q

Why does a catalyst affect the rate of a reaction?

A

A catalyst provides a alternate pathway for particles which requires less activation energy so more particles can react

55
Q

What are the advantages and disadvantages of using catalysts?

A

+ Save money -don’t need to operate as log to produce the same amount of ‘stuff’
+ Reduce the need for a high temperature (good for environment and cost
+ Can use again and again-not used up in reaction

  • Expensive to buy
  • Different reactions use different catalysts
  • Denature
56
Q

What is an exothermic reaction?

Give 3 examples…

A

An exothermic reaction gives out energy to its surroundings (rise in temperature)

Combustion; burning fuels
Neutralisation; acid + alkali –> salt + water
Oxidisation; sodium + water-heat

57
Q

What is an endothermic reaction?

Give an example…

A

An endothermic reaction takes in energy from the surroundings (usually heat-fall in temperature)

Thermal decomposition; CaCO₃ –> CaO + CO₂

58
Q

Is a reversible reaction endothermic or exothermic?

A

It can be either, if itis endothermic one direction it will be exothermic in the other; the energy absorbed by the endothermic reaction is equal to the energy released in the exothermic reaction

59
Q

What does Anhydrous mean?

A

Without water

60
Q

1) What pH is a solution with a H+ ion?

2) What is a solution with a OH- ion?

A

1) Acidic, a pH of 7-

2) A base, a pH of 7+

61
Q

What is an alkali?

A

A base that dissolves in water

62
Q

What is the neutralisation equation

A

Acid + base –> salt + water

H+ + OH- –> H2O

63
Q

1) What is the neutralisation equation for ammonia and nitrate?
2) What is the product of the reaction used for and why?

A

1) Ammonia + nitric acid –> ammonium nitrate
This is neutralization equation is different as no water is produced.
2) Ammonium nitrate; fertiliser, it has nitrogen from two sources ammonia and nitric acid - plants need nitrogen to make proteins

64
Q

1) What salt does hydrochloric acid form?

2) What salt does sulfuric acid form?

A

1) Chloride

2) Sulfate

65
Q

What does a acid and a metal oxide react to form? (It’s the same as a acid and metal hydroxide)

A

Acid + Metal oxide –> salt + water

66
Q

What do metal and acids react to form?

A

Acid + metal –> salt + hydrogen

67
Q

The concentration of a solution is measured in units of?

A

Mol/dm3

68
Q

What would you need to do to make a dry sample of a soluble salt from an insoluble base (metal oxide/metal hydroxide)?

A

Add the insoluble base to the acid until the reaction is complete; the excess solid can be seen at the bottom of the flask.
Filter out the excess solid and evaporate the water of the salt solution letting it crystallise to from a pure dry sample

69
Q

What would you need to do to make a dry sample of a soluble salt from an metal?

A

Add the metal to the acid - the solid will disolve in the acid as it reacts - until the reaction is complete; the excess solid can be seen at the bottom of the flask.
Filter out the excess solid and evaporate the water of the salt solution letting it crystallise to from a pure dry sample

70
Q

What would you need to do to make a dry sample of a soluble salt from an alkali?

A

Add a universal indicator to the acid, and add enough of the alkali till it is neutralised (pH 7 and green)
Then repeat using the same concentration and amount of both but without the universal indicator to complete a uncontaminated salt.
Evaporate off the water to crystallise the salt.

71
Q

Why can’t you just add lots of alkali to a acid to form a soluble salt?

A

Yo can’t tell when the reaction has finished

72
Q

What reaction would you need to do to make a insoluble salt?

A

A precipitation reaction

73
Q

What would you need to do to make a dry sample of a insoluble salt?

A

Chose two solutions that contain the ions needed (two soluble solutions)
React them together
Once the salt has precipitated out filter, wash and dry it

74
Q

What are the uses of precipitation reactions?

A

Remove poisonous ions from water
Remove calcium and magnesium ions from hard water
To treat sewage - remove unwanted ions

75
Q

What is electrolysis?

A

Breaking down a substance using electricity

76
Q

What is an electrolyte?

A

An molten or dissolved onic substance; contains positive and negative ions which are free to move.
The electrolyte is broken down in electrolysis.

77
Q

Why are free ions needed in electrolysis?

A

To conduct electricity - electrical circuit needs to be complete

78
Q

Where do metal ions move in electrolysis?

A

The positive metal ions move to the cathode where they gain electrons and are reduced

79
Q

Where do nonmetal ions move in electrolysis?

A

The negative nonmetal ions move to the anode where they lose electrons and are oxidised

80
Q

What will form at the anode?

A

If halide ions are present a halide will form

If halide ions aren’t present oxygen will form

81
Q

What will form at the cathode?

A

If the metal is less reactive than hydrogen the metal will form.
If the metal is more reactive than hydrogen the metal will form.

82
Q

What could you add mix to make an soluble salt?

A

Acid and insoluble base; metal oxide/hydroxide
Acid and alkali
Acid and metal

83
Q

Name three soluble acids…

A

Nitrates
Sulfates
Chlorides

84
Q

Name two insoluble bases…

A

Metal oxide

Metal hydroxide

85
Q

What does ammonia dissolve in water to produce?

A

Ammonia dissolves in water to produce an

alkaline solution. It is used to produce ammonium salts. Ammonium salts are important as fertilisers

86
Q

Why when making a soluble salt using a metal, are not all metals suitable?

A

Some are too reactive and some are not reactive enough

87
Q

Describe electrolysis

A

When an ionic substance is melted or dissolved in water, the ions are free to move about within the liquid or solution.

Passing an electric current through ionic substances that are molten or in solution breaks them down into elements.

This process is called electrolysis and the substance that is broken down is called the electrolyte.

During electrolysis, positively charged ions move to the negative electrode, and negatively charged ions move to the positive electrode.

Chemistry (5 decks)

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