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Chemistry > Unit 1 - PPQ > Flashcards

Unit 1 - PPQ Flashcards

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1
Q

Give two reasons why the first standard molar ionisation energy for potassium is much less than that of argon. [2]

A

Electron removed from energy level further from nucleus

Increased shielding for potassium

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2
Q

Give a reason why the value for the second standard molar ionisation energy of potassium is larger than that of argon. [1]

A

nuclear charge for K is greater

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3
Q

State how you would explain to the general public how the pH scale is used to describe levels of acidity. [2]

A

Acidic solutions have pH <7

Lower the figure, higher the degree of acidity

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4
Q

SO2 (aq) + H2O(l) ⇌ H+(aq) + HSO3-(aq)

Explain why sulphur dioxide is described as an acidic oxide [1]

A

H+ ions are produced

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5
Q

Explain what is meant be dynamic equilibrium [1]

A

Rate of forward reaction equals the rate of reverse reaction

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6
Q

SO2 (aq) + H2O(l) ⇌ H+(aq) + HSO3-(aq)
Use Le Chatelier’s principle to explain how the concentration of hydrogen ions, H+(aq), would change if more sulfur dioxide were dissolved in a solution that had reached dynamic equilibrium. [2]

A

[H+] would increase

Increase in conc. of reactants moves position of eqm to the right

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7
Q

S O 2–(aq) + 2I–(aq) 2SO 2–(aq) + I (aq)

Suggest a method of measuring the rate of this reaction. [1]

A

Colorimetry

- measure intensity of red-brown colour of Iodine, over time

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8
Q

Give an example of a process that uses a heterogeneous catalyst, stating the process and the name of the catalyst.

A

Haber Process

Iron(III)

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9
Q

Define standard condition [1[

A

298K and 1 atm

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10
Q

State Hess’s Law [1]

A

Enthalpy change in a reaction is independent of the route taken

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11
Q

Explain why spectrum is seen as series of sharp lines and not as a continuous spectrum [2]

A

Energy levels are quantised so only certain frequencies are allowed

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12
Q

State the relationship between energy, frequency and wavelength [2]

A

E=hf

c=fλ - f∝λ-1

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13
Q

Explain meaning of relative isotopic mass [2]

A

mass of atoms on an isotope of an element relative to mass of atoms in carbon isotope 12C

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14
Q

Explain how relative atomic mass differs from relative isotopic mass [1]

A

Relative isotopic mass only considers one isotope, but the relative atomic mass considers a weighted average of the isotopes present.

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15
Q

This solution was too concentrated for a normal titration and they needed to dilute it exactly ten times using water.
Describe, stating the apparatus used and any essential details, how this dilution was done. 3
You should assume that you need 250 cm of the diluted solution. [4]

A

Measure out exactly 25.0 cm3 using a pipette
Add this to a (250 cm3) volumetric flask
Dilute with distilled water and make up to the mark
Use dropping pipette for making up to the mark
Shake the mixture a number of times to ensure thorough mixing

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16
Q

Explain how you would tell, from properties of system, equilibrium had been reached [1]

A

No change in amount of each species present

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17
Q

Explain term isotopes [1]

A

Atoms with same atomic number bit different mass number

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18
Q

Explain term half life [1]

A

Time taken for for number of radioactive nuclei to fall to half its initial value

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19
Q

State Le Chatelier’s Principle [1]

A

If a system in equilibrium is subjected to a change in pressure, concentration or pressure, the position of equilibrium will shift to minimise the effect of that change

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20
Q

Define term acid [1]

A

Proton donor

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21
Q

Explain how CO2 can behave as an acid [1]

A

Reacts with water to produce H+ ions

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22
Q

Though the pH of pure water is 7, explain why naturally-occurring water in contact with air has a pH of less than 7. [1]

A

CO2 from air will produced H+ ions which will make water acidic

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23
Q

Explain the term relative atomic mass [2]

A

average mass of one atom of the element relative to 1/12th mass of one atom of C-12

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24
Q

State how potassium ions are formed in a mass spectrometer [1]

A

Gaseous atoms bombarded with high energy electrons

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25
Q

State how K+ ions are separated in a mass spectrometer [1]

A

Deflected through a magnetic field

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26
Q

Explain term molar first ionisation energy [2]

A

Enthalpy change for the formation of one mole of single positive charge gaseous ions from gaseous atoms under standard conditions

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27
Q

Explain why K has lower first IE than Na [2]

A

Greater shielding of outer e- in K which outweighs larger nuclear charge
Na outer electron is closer to nucleus

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28
Q

Explain why there’s large difference between first and second IE of K [2]

A

Shielding effect on outer electron is less

2nd electron removed from inner shell closer to nucleus

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29
Q

Explain why raising temperature by a small amount causes rate of chemical reaction to increase by a large amount [1]

A

Fraction of molecules that have required Ea is much greater at a higher temperature

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30
Q

CO2(g)⇌ CO2(aq)
When the top is removed from a bottle of fizzy drink it goes ‘flat’ because much of the dissolved carbon dioxide comes out of solution.
Explain why this happens in terms of chemical equilibria. [2]

A

Concentration of CO2(g) falls so position of eqm shifts to left so concentration of CO2(aq) falls

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31
Q

Explain why lines become closer together at high frequency end of spectrum [1]

A

Energy levels of H atom become closer

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32
Q

In ΔH experiment, explain why extrapolation gives a more accurate temperature change than using
the maximum temperature recorded in the experiment. [1]

A

Extrapolation gives the temperature that would have been reached if the reaction occurred instantly

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33
Q

Explain how a catalyst increases the rate of a chemical reaction. [2]

A

Catalysts provide an alternative route with a lower activation energy

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34
Q

. Explain why temperature affects the rate of a chemical reaction. [3]

A

At higher temperatures particles have more energy
More collisions have energy above activation energy
Successful collisions occur more frequently

35
Q

State the effect of using a catalyst on the position of equilibrium. [1]

A

No effect

36
Q

Explain why helium has a higher first ionisation energy than hydrogen [2]

A

Greater nuclear charge on He

No increase in shielding

37
Q

Explain why nitrogen has a higher first ionisation energy than oxygen [2]

A

Outer electron in O is paired in orbital

Repulsion between paired electrons makes it easier to remove outer e-

38
Q

Explain how the lines in the atomic emission spectrum are formed. [3]

A

Electrons excited to higher energy level
Energy levels are quantised
Electrons drop from higher to lower energy levels
Energy emitted as light

39
Q

Explain how the ionisation energy of a hydrogen atom can be calculated from a feature in the atomic emission spectrum. [3]

A

Find frequency of convergence limit for human series

IE given by E = hf

40
Q

State what is meant by γ-radiation and why it cannot be identified from the information given in the scheme.[2]

A

γ radiation is high energy electromagnetic radiation

Affects neither atomic or mass number

41
Q

Explain why zinc powder is used in ΔH experiment rather than pieces of zinc metal. [2]

A

Powder has greater surface area so gives higher rate of reaction

42
Q

Give a reason why the sign of the enthalpy value calculated is different from the sign of the temperature change measured. [1]

A

Enthalpy measures chemical energy and as heat energy increases, chemical energy must decrease

43
Q

State what is meant by an α-particle. [1]

A

A helium (atom) nucleus

44
Q

How would you explain the meaning of the pH scale to a member of the public? [3]

A

The pH scale runs from 0-14
pH<7 = acid />7 = alkali
acid stronger as pH value decreases

45
Q

State the meaning of the word heterogeneous. [1]

A

catalyst in different physical state to reactants

46
Q

State why relative molecular mass has no units [1]

A

It’s is a relative quantity based on 1/12th of the 12C atom as one unit

47
Q

State what is meant by β-emission. [1]

A

An electron formed when a neutron changes into a proton

48
Q

Give the full electronic configuration of a nitrogen atom and use this to describe the way in which electrons are arranged in atoms. [4]

A

Electrons within atoms occupy fixed energy levels or shells of increasing energy
1s2 2s2 2p3
The first shell in nitrogen has s orbitals and the second shell s and p orbitals
maximum of two electrons can occupy any orbital with opposite spins
Orbitals of the same type are grouped together as a sub-shell
Each electron fills one orbital before paiting

49
Q

Describe the main features of the atomic emission spectrum of hydrogen in the visible region. Explain how these features arise and how their interpretation provides evidence for energy levels in the atom. [6]

A

Atomic spectrum of hydrogen is a series of lines that get closer as their frequency increases
Lines arise from electrons being excited by absorbing energy
electron jumping up to a higher energy level and falling back down and emitting energy in the form of
EM radiation to the n = 2 level
Since lines are discrete energy levels must have fixed values

50
Q

Suggest why compounds containing B3+ ions are unlikely to exist. [1]

A

Too much energy required to form B3+ ion

51
Q

State how the first three ionisation energies of calcium would differ from those of potassium. [2]

A

Value of 1st and 3rd I.E. will be higher (1)

Value of 2nd I.E. will be smaller

52
Q

Explain why the use of catalysts provides economic and environmental benefits. [3]

A

Lower temp can be used
Energy costs saved
More product made in a given time
Enable reactions to take place that would be impossible otherwise

53
Q

Explain the term atomic number [1]

A

Number of protons in nucleus

54
Q

Explain term isotope [1]

A

Same number of protons but different number of neutrons

55
Q

State what could be done to solid copper to increase rate of its reaction with HCl [1]

A

Crush it into powder form to increase its surface area

56
Q

Explain why helium has higher first IE than neon [2]

A

In He, less shielding of outer electron outweighs smaller nuclear charge
He outer electron is closer to nucleus

57
Q

Explain why neon has higher first IE than nitrogen [1]

A

Ne has greater nuclear charge

58
Q

Explain why nitrogen has higher first IE than oxygen [2]

A

N only has unpaired 2p electrons whereas O has 2 unpaired and 2 paired 2p electrons
Pairing results in mutual repulsion, making it easier to remove one of the electrons

59
Q

Explain how a catalyst speeds up a reaction [2]

A

Provides new route of lower activation energy

60
Q

What type of catalyst is iron in the Haber Process [1]

A

Heterogenous

61
Q

Write an equation for the acid-base reaction of ammonia with sulphuric acid [1]

A

NH3 + H2SO4 -> (NH4)2SO4

62
Q

Explain why hydrogen emits only certain definite frequencies of visible light [2]

A

Electron falls from higher energy levels to lower energy levels
Energy emitted is related to the frequency -> E=hf

63
Q

In the mass spectrum, explain why peaks due to hydrogen atoms are present, although hydrogen gas contains only H2 molecules. [1]

A

Some of the H2 is split into atoms

64
Q

Give two reasons why the use of gas to generate electricity does not match the definition of sustainability. [2]

A

Increases CO2 levels which causes global warming

Gas is a non-renewable energy source

65
Q

Suggest one method of generating electricity which would be sustainable and outline how it works. [2]

A

Wind

- rotation of blades turns turbine

66
Q

State two common sources of error in titration experiments [2]

A

Overshooting
Funnel left in burette
Solution in flaks not mixed thoroughly

67
Q

State the significance of the frequency of convergency limit in the Lyman series [1]

A

Energy needed to ionise the atom

68
Q

Explain why there is more than one series of lines [1]

A

In each series, the excited electron drops back to different energy level

69
Q

Explain briefly the origin of atomic spectra in terms of electron transitions [2]

A

electrons absorb energy from radiation
excited up to higher energy level
leaves dark lines in spectrum

70
Q

Describe the visible emission spectrum of a hydrogen atom and explain, in terms of the atom’s electronic structure, why it does not consist of a continuous, rainbow-like spectrum. [3]

A

Series of sharp lines on dark background, converging towards violet end
Atoms electron energy levels have fixed values
Lines arise when electrons fall between energy levels and thus have fixed energies and wavelengths

71
Q

Give 2 uses of radioactive materials in analysis, industry or medicine [2]

A

Cobalt 60 - Cancer treatment
Carbon 14 - radio carbon dating
Iodine 131- tracer in thyroid glands

72
Q

Describe what is meant by atom economy [1]

A

Amount of % by mass of all reactants that ends up in desired product

73
Q

Describe in simple terms what is meant by pH. [1]

A

Measure of acidity/alkalinity of aqueous solution

74
Q

Name three factors that can affect the rate of chemical reaction [3]

A 
temperature
Pressure
Catalyst
Light
particle size
75
Q

State what is meant by the average bond enthalpy of an O––H bond and explain why the word average must be used [2]

A

The average energy needed to break OH bond

OH bonds in different molecules will have slightly different bond energies and so a mean/average = more useful

76
Q

Give reason why it’s necessary to ionise atoms in sample in a mass spectrometer [1]

A

To be able to accelerate ions so they can be deflected by magnetic field

77
Q

The first compound of a noble gas was formed from Xe atoms and PtF6. It was the ionic compound Xe+ PtF6–.
Explain why it is not possible to form a similar ionic compound of argon, Ar+ PtF6–. [2]

A

Compound formation has noble gas atom being ionised

IE of argon is much higher than that of Xenon because outer electron in argon is closer to nucleus

78
Q

In which part of the electromagnetic spectrum does the Balmer Series appear? [1]

A

Visible region

79
Q

Without altering the shape of the mass spectrometer, what change could be made to allow ion Y, with its higher mass to charge ratio, to pass through the slit and be detected? [1]

A

Increase strength of magnetic field

80
Q

In terms of bond strengths, explain why enthalpy changes of combustion are negative. [1]

A

energy in bonds broken is less than

that in bonds made

81
Q

State what is meant by molar mass. [1]

A

Mass of one mole of compound

82
Q

Suggest why no more than the minimum energy is used to ionise the sample of lithium. [1]

A

So that only 1 electron is knocked out

83
Q

State the difference, if any, between the chemical properties of the isotopes 6Li and 7Li, giving a reason for your answer. [2]

A

No difference

Same number of electrons in outer shell

84
Q

Define the term activation energy [1]

A

Minimum energy required by molecules for them to react

Chemistry (2 decks)

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