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A-Level Chemistry [OCR B] (updated: > Developing Fules > Flashcards

Flashcards in Developing Fules Deck (50)
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1
Q

[DF1] What is the ideal gas equation?

A

pV = nRT

p: pressure (Pa)
V: volume (m³)
n: number of moles (mol)
R: gas constant (8.313 J mol⁻¹ K⁻¹)
T: tempreture (K)
2
Q

[DF1] How can you predict the yield of a reaction?

A

(e.g. 4Na + O₂ → 2Na₂O)

  • Work out the number of moles of a reactant you have used.
    (for 2g of Na: 2/23 = 0.087 mol)
  • Multiply by the ratio between the chosen reactant and product.
    (0. 087 x 0.5 = 0.044 mol)
  • Multiply by the Mᵣ of the product.
    (0. 044 x 62 = 2.73g)
3
Q

[DF2] What is the difference between a π bond and a σ bond?

A

A σ bond is caused by the direct overlap of the p-orbitals or carbon atoms.

π bonds are caused by the indirect ‘leaning overlap of p-orbitals.

https://drive.google.com/file/d/1SoOShMkBMVTeTVWXH3FekXELkqsEf-dH/view?usp=sharing

4
Q

[DF2] What is a double bond?

A

A double bond consists of one π bond and one σ bond.

5
Q

[DF2] How can you draw a molecule in 3D?

A
  • A solid line represents a bond in the plane of the paper.
  • A solid wedge represents a bond coming out of the plane of the paper.
  • A dashed/dotted wedge represents a bong going into the plane of the paper.
6
Q

[DF3] What is the meaning of the term ‘endothermic’?

A
  • Endothermic reactions are those that take energy in from the surroundings:
  • The energy needed to break the bond is greater than the energy needed to make the bond in the reaction.
7
Q

[DF3] What is the meaning of the term ‘exothermic’?

A
  • Exothermic reactions are those that release energy into the surroundings:
  • The energy needed to break the bond is less than the energy needed to make the bond in the reaction.
8
Q

[DF3] What are standard conditions?

A
  • A pressure of 100kPa (1atm)
  • A temperature of 298K (room temperature)(25⁰C)
  • All solutions are at a concentration of 1 mol dm⁻³ for electrode potentials.
9
Q

[DF3] Define the standard enthalpy change of reaction, ΔHᵣᶿ.

A

The enthalpy change that occurs when substances are reacted in the molar ratios as defined by a chemical equation.

The reaction takes place under standard conditions with reactants and products in their standard states.

10
Q

[DF3] Define the standard enthalpy change of combustion, ΔH꜀ᶿ.

A

The enthalpy change that occurs when substances are reacted with one mole of oxygen.

The reaction takes place under standard conditions with reactants and products in their standard states.

11
Q

[DF3] Define the standard enthalpy change of formation, ΔHғᶿ.

A

The enthalpy change that occurs when one mole of a compound is formed from its constituent elements in their standard states under standard conditions.

12
Q

[DF3] Define the standard enthalpy change of formation, ΔHₙₑᵤₜᶿ.

A

The enthalpy change that occurs when one mole of water is produced from a neutralisation reaction that happens under standard conditions.

13
Q

[DF3] What is average bond enthalpy?

A

The energy needed to break one mole of the standard bond under standard conditions.

14
Q

[DF3] What relation does bond enthalpy have to bond strength?

A

The greater the bond enthalpy, the greater the bond strength.

As the bond strength increases the length of the bond decreases.

15
Q

[DF3] Match the reaction process to the thermal result:

  • Bond breaking.
  • Bond making.
  • Exothermic.
  • Endothermic.
A
  • Bond breaking = Endothermic.

- Bond making = Exothermic.

16
Q

[DF3] What does each term mean in q = mcΔT

A

q = mcΔT

q: The energy absorbed by the material (normally water) (J)
m: The mass of material being used (g)
c: The specific heat capacity of the material used (c of water = 4.18 Jg⁻¹K⁻¹)
ΔT: The change in temperature of the material (final - initial)

17
Q

[DF4] What is a catalyst?

A
  • A catalyst is a substance that is not used up in the reaction.
  • And helps to increase the rate of reaction by offering a different pathway for the reaction to take.
18
Q

[DF4] What is catalyst poison?

A

A substance that reduces the effectiveness of the catalyst by permanently bonding to the active site.

19
Q

[DF4] What does heterogeneous mean?

A
  • A heterogeneous catalyst is one that does not share the same phase as the reactants.
  • For example the solid iron catalyst in the gaseous reaction of hydrogen and nitrogen.
20
Q

[DF4] What does heterogeneous catalysis look like?

A
  • The reactants form partial bonds with the catalyst, adsorbing onto the surface.
  • Because the reactants are in close proximity, successful collisions are more frequent.
21
Q

[DF4] What is cracking?

A

The breaking of long-chain alkanes into shorter-chain alkanes and alkenes.

22
Q

[DF5] What are some common simple molecular pollutants?

A
  • CO.
  • CO₂.
  • NOₓ.
  • SOₓ.
  • unburnt hydrocarbons.
23
Q

[DF5] What are some methods of reducing CO₂ emissions?

A

Using renewable sources of electricity such as solar or wind power as well as using electric or hydrogen-powered cars can be methods of reducing CO₂ emissions.

24
Q

[DF5] What are some methods of reducing CO and unburnt hydrocarbons?

A

Using more efficient engines and catalytic converters in cars.

25
Q

[DF5] How can NOₓ and SOₓ emissions be reduced

A

Modifications to engines and the fuels used can reduce NOₓ and SOₓ emissions.

26
Q

[DF6] What is an aromatic hydrocarbon?

A

A hydrocarbon that contains benzene (or other aromatic) ring.

27
Q

[DF6] What is an aliphatic hydrocarbon?

A

A hydrocarbon that does not contain any aromatic rings and is a straight or branched chain hydrocarbon

28
Q

[DF6] What is a saturated hydrocarbon?

A

A hydrocarbon which contains only single carbon-carbon bonds.

29
Q

[DF6] What is an unsaturated hydrocarbon?

A

A hydrocarbon which contains one or more carbon=carbon double bond.

30
Q

[DF6] What is a homologous series?

A

A group of hydrocarbons with the same functional group and thus the same general formula.

(each successive member differs by CH₂.)

31
Q

[DF6] What is a functional group?

A

A functional group is a group of atoms on a carbon chain that gives the molecule its properties.

32
Q

[DF7] What is the difference between complete and incomplete combustion?

A

Incomplete combustion occurs when there is not enough oxygen present, it produces carbon monoxide and carbon particulate (soot).

33
Q

[DF7] Complete the following complete combustion reaction:

CH₄ + 2O₂ →

A

CH₄ + 2O₂ → CO₂ + 2H₂O

34
Q

[DF7] Balance the following incomplete combustion reactions:

C₃H₈ + _O₂ → 3C + 4H₂O

C₃H₈ + _O₂ → 3CO + 4H₂O

A

C₃H₈ + 2O₂ → 3C + 4H₂O

C₃H₈ + ⁷/₂O₂ → 3CO + 4H₂O

35
Q

[DF7] Complete the following reaction:

Ethene + Bromine →

A

Ethene + Bromine → 1,2-Dibromoethane

36
Q

[DF7] Complete the following reaction:

Propene + Hydrogen Bromide →

A

Propene + Hydrogen Bromide → 1-bromopropane OR 2,bromopropane

37
Q

[DF7] What catalyst is used in:

C₂H₄ + H₂ →

A

Nickle Catalyst - finely divided

C₂H₄ + H₂ → C₂H₆

38
Q

[DF7] Compete the following reaction with its required conditions:

C₂H₄ + H₂O →

A

Phosphoric acid catalyst (H₃PO₄)
300⁰C
60 atm

C₂H₄ + H₂O → C₂H₅OH

39
Q

[DF8] What is the repeat unit of the polymer formed by the addition polymerisation of ethene?

A

-(C₂H₄)ₙ-

40
Q

[DF8] What is the name of this polymer?

-(C₂H₄)ₙ-

A
  • poly(ethene)

- Common name: polythene

41
Q

[DF9] What is an electrophile?

A

An electrophile is a substance that accepts a lone pair of electrons in a reaction.

42
Q

[DF9] What is a carbocation?

A
  • A carbocation is a hydrocarbon that contains a positively charged carbon atom.
  • It is normally unstable and occurs as an intermediate in electrophilic addition.
43
Q

[DF9] How are organic mechanisms confirmed empirically?

A

The products of the reaction are analysed when different anions are used in the reaction.

44
Q

[DF10] What are structural isomers?

A

Structural isomers are hydrocarbons with the same molecular formula, but different structural formulae.

45
Q

[DF10] What are stereoisomers?

A

Stereoisomers are hydrocarbons with the same structural formula, but different arrangements in their atoms in 3D space.

46
Q

[DF10] Why does stereoisomerism occur around a double bond?

A

Free rotation is restricted around the double bond.

When each carbon has two different groups attached to it different arrangements are possible about the C=C bond.

47
Q

[DF10] What is cis-trans isomerism?

A

Cic-trans isomerism is a type of E-Z isomerism that occurs when each carbon in the double bond has one group in common.

48
Q

[DF11] What are some benefits of using fossil fuels?

A
  • Fossil fuels are readily available due to all the infrastructure to use them already being in place.
  • Fossil fuels are cheaper than alternatives.
  • Fossil fuels are very efficient at producing energy: they have a high energy destiny.
49
Q

[DF11] What are some risks of using fossil fuels?

A
  • Burning fossil fuels causes greenhouse gases to be released which contributed greatly to global warming.
  • Burning fossil fuels causes air pollutants to be released which pose a health risk to humans.
  • Fossil fuel reserves are limited and may start to run out in the near future.
50
Q

[DF7] What does δ mean?

A

Very small enthalpy change.