Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

OCR(B) Chemistry > DF From Sep 2015 > Flashcards

DF From Sep 2015 Flashcards

1
Q

What is an endothermic reaction?

A

A reaction that takes in energy and cools and surroundings - the overall energy change is positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a chemical bond?

A

It is an electrical attraction between atoms or ions and therefore requires energy in order for the bond to break in order to overcome the attractive forces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is bond enthalpy?

A

It is the quantity of energy needed to break a particular bond in a molecule, also called bond dissociation enthalpy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is average bond enthalpy?

A

The average quantity of energy needed to break a particular bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Does a higher bond enthalpy mean a shorter bond length?

A

Yes, it means more attraction between nuclei and the electrons so greater attractive forces.
Greater attractive forces mean a smaller bond length because it takes longer for repulsive forces to balance it.
The shorter bond length means a larger bond enthalpy because there is greater attractive forces to overcome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Is bond breaking or bond making exothermic?

A

Bond making is exothermic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the standard enthalpy change for a reaction?

A

The enthalpy change when molar quantities of reactants as stated in the equation react together under standard conditions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the standard conditions for standard enthalpy change?

A

1 atm (pressure)
298K (temperature)
All the substances in their standard states.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the equation for measuring enthalpy changes?

A

Energy transferred = specific heat capacity x mass x change in temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the standard enthalpy change of combustion?

A

The enthalpy change that occurs when one mole of a substance is burnt completely in oxygen under standard conditions in standard states.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the standard enthalpy change of formation?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the standard enthalpy change of neutralisation?

A

The enthalpy change when one mole of hydrogen ions react with one mole of hydroxide ions to form one mole of water under standard conditions and in solutions containing 1moldm^-3.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is an exothermic reaction?

A

A reaction that gives out energy and heats the surroundings - an overall negative energy change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Give at least 3 disadvantages of Biofuels

A

Loss of Biodiversity
Non-food crops make food scarce / more expensive
Deforestation
Depletion of soil nutrients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Give advantages of biodiesel over fossil fuel diesel

A

Can be made from waste vegetable oil
Carbon neutral (excluding energy for harvesting, processing and distributing the fuel)
It is biodegradable
No sulphur (so no sulphur dioxide/acid rain)
Less particulates
Less Carbon Monoxide
Less unburned hydrocarbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Give advantages of using hydrogen as a fuel

A

Renewable via hydrolysis of water
Can be sent down natural gas pipelines
Can be used in internal combustion engine or in fuel cells
When burnt, only forms water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Give disadvantages of using hydrogen as a fuel

A

Electrolysis might use fossil fuel electricity source
Less energy dense than petrol and diesel
Sometimes produced from methane (fossil fuel source)
Can produce NOx in internal combustion engine (acid rain)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Convert the following:

1) cm^3 to m^3
2) dm^3 to m^3
3) °C to K
4) kPa to Pa

A

1) x10^-6
2) x10^-3
3) +273
4) x10^3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How many moles of gas occupy 3027 cm^3 at 25°C and 400kPa?

A

1) convert units:

3027cm^3 = 0.003027 m^3
25°C = 298K
400kPa = 400000 Pa

2) rearrange pV=nRT to n = pV/RT
3) substitute in values:
400000x0. 003027 / 8.314x298

= 0.4889….. moles

n = 0.488 moles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is the volume of 1 mole of gas at 200 kPa and 23 °C

A

1) convert units:

200kPa = 200000 Pa
23°C = 296 K

2) rearrange pV=nRT

V= nRT/p

3) substitute in values:
8. 31x1x296/200000

= 0.1231…

V= 0.0123 M^3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Define Hess’ Law

A

As long as the starting and finishing points are the same, the enthalpy change will always be the same, irrespective of how you get from start to finish.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is an aromatic compound?

A

Compounds that contain one or more benzene rings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is an aliphatic compound?

A

Compounds that do not contain any benzene rings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is a functional group?

A

Modifiers that are responsible for the characteristic chemical reactions of molecules.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Define the word ‘saturated’.

A

Hydrocarbons containing the maximum number of hydrogen atoms possible, no carbob-carbon double or triple bonds.

26
Q

What is a homologous series?

A

A series of compounds in which all members have the same general molecular formula.

27
Q

What is the general molecular formula for alkanes?

A

CnH2n+2

28
Q

What is the general molecular formula for alkenes?

A

CnH2n

29
Q

What is the general molecular formula for cycloalkanes?

A

CnH2n

30
Q

What is a carbocation?

A

An ion with a positively-charged carbon atom.

31
Q

What is an isomer?

A

Two molecules that have the same molecular formula but differ in the arrangement of atoms. They are compounds with different physical properties and often different chemical properties too.

32
Q

What is a structural isomer?

A

The atoms are bonded together in a different order in each isomer.

33
Q

What is a stereoisomer?

A

The order of bonding in the isomer is the same, the arrangement of the atoms in space is different in each isomer.

34
Q

What is chain isomerism?

A

It is a type of structural isomerism. When an alkane has four or more carbon atoms different arrangements. E.g. Butane and methylpropane.

35
Q

What is position isomerism?

A

It is a type of structural isomerism. Position isomerism occurs when the functional group is situated in different positions in the molecules.

36
Q

What is functional group isomerism?

A

It is a type of structural isomerism. It is sometimes possible for compounds with the same molecular formula to have different functional groups.

37
Q

What is E/Z isomerism?

A

E (entgegen) means opposite. Z (zusammen) means together. E and Z isomers are different compounds so they have different properties.

38
Q

How do you name alcohols?

A
  1. Name the alcohol using the root prefix of the longest chain.
  2. Determine the position of the alcohol group (-OH) by counting the carbons.
  3. Add ‘ol’ on the name.
39
Q

What are enthalpy cycles used for?

A

When the direct route of the reaction cannot be measured, so the indirect route is used. This route involves two enthalpy changes, both of which can be measured easily.

40
Q

How are enthalpy changes of combustion used to work out overall enthalpy change?

A

Enthalpy change in combustion means one mole of the substance reacts with oxygen to form oxides. E.g. C becomes CO2 and H2 becomes H2O.
ΔcH1 is the enthalpy change of the reaction
ΔcH2 is the enthalpy change of combustion of reactants
ΔcH3 is the enthalpy change of combustion of products
ΔcH1=ΔcH2-ΔcH3

41
Q

What is an Aromatic compond?

A

Compuonds that contain one or more benzene rings.

42
Q

What is an Aliphatic compound?

A

Compounds that do not contain any benzene rings.

43
Q

What is a functional group?

A

Modifiers that are responsible for the characteristic chemical reactions of molecules.

44
Q

What is a Homologous series?

A

A series of compounds in which all members have the same general molecular formula.

45
Q

What goes in and out of a car engine?

A

IN: Fuel, air.
OUT: CO2, CO, H2O, CxHy (hydrocarbons), SOx (sulfur oxides), N2, NOx (nitrogen oxides), particulates.

46
Q

How are sulfur oxides formed?

A

Sulfur compounds in the fuel (impurities) reacting with O2 in the air.

47
Q

How are nitrogen oxides formed?

A

Nitrogen oxides are formed by components in the air reacting.

48
Q

How is carbon monoxide formed?

A

CO is formed by incomplete combustion of hydrocarbons.

49
Q

Define “primary pollutant”.

A

A pollutant released directly into the atmosphere. (e.g. carbon dioxide)

50
Q

Define “secondary pollutant”.

A

A pollutant made by reactions of primary pollutants. (e.g. ozone)

51
Q

Sources/effects of particulates are…

A

SOURCES; volcanoes, burning fuels, burning coal

EFFECTS: heart attacks, lung cancer

52
Q

Sources/effects of volatile organic compounds (VOC) are…

A

SOURCES: plants, unburnt fuel from petrol engines
EFFECTS: photochemical smog

53
Q

Sources/effects of carbon monoxide are…

A

SOURCES: incomplete combustion of hydrocarbons, burning biomass
EFFECTS: toxic gas, photochemical smog

54
Q

Sources/effects of carbon monoxide are…

A

SOURCES: combustion of fossil fuels
EFFECTS: greenhouse gas (global warming)

55
Q

Sources/effects of nitrogen oxides are…

A

SOURCES: fuel combustion in power stations/vehicles
EFFECTS: acid rain, photochemical smog

56
Q

Sources/effects of sulfur oxides are…

A

SOURCES: volcanoes, burning fuels containing sulfur
EFFECTS: toxic gas, acid rain

57
Q

Incomplete combustion of hydrocarbons leads to?

A

Products of WATER, and either CARBON MONOXIDE or CARBON.

58
Q

Incomplete combustion of alcohols leads to?

A

Products of WATER, and either CARBON MONOXIDE or CARBON. (same as hydrocarbons!)

59
Q

How are enthalpy changes of formation used to work out overall enthalpy change?

A

Enthalpy change in formation means one mole of a compound is formed from its elements.
Enthalpy change of reaction=enthalpy change of formation of products-enthalpy change of formation of reactants
ΔrH1=ΔrH3-ΔrH2

60
Q

Why do N2 and O2 only react in a car engine?

A

The NN bond is very strong and only the temperatures in the car engine can give the N2 molecules enough kinetic energy to break the NN bond and react with O2

OCR(B) Chemistry (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions