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Chemistry > Everything > Flashcards

Everything Flashcards

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1
Q

Explain how geometric isomerism arises in but-2-ene.

A

The double bond is formed by overlap of adjacent p-orbitals

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2
Q

Explain why atom economy for formation of 2-bromobutane is different for each reaction.

A

Atom economy with but-2-ene is 100%

With but-1-ene some 1-bromobutane forms so it is less than 100%

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3
Q

Name the product if the reaction between but-2-ene and acidified potassium manganate.

A

2,3-butandiol

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4
Q

State a problem associated with the disposal of used polymer products.

A

They are not biodegradable

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5
Q

State one way in which the use of polymers can be made more sustainable.

A

Recycling
Reusing
Using renewable energy sources in their production
Using chemicals from plants

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6
Q

The reaction of methane and chlorine is a free radical substitution.
State the essential condition for this reaction.

A

Ultraviolet radiation

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7
Q

Explain fully what a curly half arrow represents in a free radical mechanism.

A

A single electron

Transferring from a bond to an atom

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8
Q

Explain why the amount of chloromethane formed in a propagation stage is much greater than the amount made in the termination stage.

A
  1. Free radicals are generated in propagation
  2. Propagation stage keeps repeating
  3. In termination two radicals form one product
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9
Q

Define standard enthalpy change of combustion.

A
  1. Energy change
  2. When 1 mole of substance combusts
  3. Completely under standard conditions
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10
Q

Write the chemical equation for the formation of nitric acid.

A

H2SO4 + NaNO3 ———> HNO3 + NaHSO4

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11
Q

Suggest why nitric acid needs to be stored in brown glass bottles.

A

To prevent it reacting in sunlight

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12
Q

Outline the steps required to determine the percentage of gold in an alloy of gold, silver and copper.

A
  1. Dissolve in excess nitric acid
  2. Filter, wash and dry
  3. Weigh allow at start and weigh gild at end
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13
Q

Write the ionic equation for the formation of magnesium nitrate and hydrogen.

A

Mg (s) + 2H+ (aq) ———> Mg2+ (aq) + H2(g)

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14
Q

Explain why cyclooctane is added to petrol.

A

It has higher octane rating

This gives more efficient combustion

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15
Q

How does the addition of a catalyst lower the temperature required for a reaction?

A
  1. Lowers activation energy
  2. By providing alternative pathway
  3. Same no. Of particles can react at lower temp
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16
Q

(Graphite)

Identify weak intermolecular forces and describe how they arise.

A
  1. London forces
  2. Instantaneous dipole due to electron distribution
  3. Induced dipole in adjacent layers
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17
Q

Suggest why a very high temperature and high pressure are needed to convert graphite to diamond.

A
  1. Equilibrium shifts right
  2. Reaction is more endothermic
  3. High pressure favours higher density
  4. High temp and pressure needed because activation energy is high
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18
Q

Explain why ionisation is an endothermic process.

A

To overcome electrostatic attraction of for electrons

19
Q

Describe the trend in first 4 ionisation energies for aluminium.

A
  1. Gradual increase in first 3 energies
  2. Big jump from 3 to 4
  3. Group 3
20
Q

Why are orbitals of the same sub shell occupied singly by electrons before paring of electrons occurs?

A

Electrons in the same orbital repel each other

21
Q

A sulfur atom can expand its octet but an oxygen atom cannot.
Suggest why this is so.

A
  1. Sulfur has 3d orbitals that can be occupied

2. Oxygen is in Period 2 and has no available d orbitals

22
Q

Deduce the shape of a sulfur dioxide molecule and suggest the bond angle.

A
  1. Bent

2. 104.5

23
Q

Outline how a solid sample of element X is converted into ions in a mass spectrometer.

A
  1. Vapourised

2. Atoms bombarded with high energy electrons

24
Q

Following formation of ions there are three steps in the production of a spectrum in the mass spectrometer.
Name the steps in order and state how the first 2 are carried out.

A
  1. Acceleration - ions passed through electric field
  2. Deflection - ions pass through magnetic field
  3. Detection
25
Q

State what is meant by a covalent bond.

A

Strong electrostatic attraction between two nuclei and shared pair of electrons

26
Q

What is the bond angle in BF3?

A

120

27
Q

How is a dative covalent bond formed?

A
  1. Donation of lone pair

2. To the atom which is electron deficient

28
Q

Explain why 1st ionisation energy of H2 is less than He but more than Li.

A
  1. He more protons than H
  2. He outer electron in same shell as H
  3. Li outer electron in higher energy level
  4. Shielded by inner electrons
29
Q

Hydrogen can be placed in several different positions in periodic tables.
Criticise the position of hydrogen immediately above lithium.

A
  1. H has 1 electron in s orbital
  2. Rest of group 1 are alkali metals
  3. Hydrogen doesn’t react in same way
30
Q

Addition of barium chloride to one of the test tubes gave a white precipitate.
Identify two possible anions.

A

SO4 (2-)

CO3 (2-)

31
Q

Explain why iodine and chlorine have many similar chemical reactions.

A
  1. 7 electrons in outer shell

2. Number of electrons in outer shell determine chemical reactions

32
Q

What are the oxidation numbers for:
S2O3 (2-)
SO4 (2-)
S4O6 (2-)

A
  1. 2+
  2. 6+
  3. 2.5+
33
Q

Write the ionic half equation for the reaction of aqueous S2O3 (2-) to give SO4 (2-).

A

S2O3 (2-) + 5H2O ——> 2SO4 (2-) + 10H+ + 8E-

34
Q

Explain why the ions in sodium fluoride are described as isoelectronic.

A

Same electronic configuration

35
Q

Explain how changes in the cation affect bond strength in an ionic compound.

A
  1. Higher the charge on cation the stronger the attraction between ions
  2. Smaller the radius of cation the stronger the attraction between ions
  3. Li+ is smaller than K+
36
Q

Explain why diamond and sodium chloride have high melting points.

A
  1. Diamond - strong attractive forces between C atoms need to be broken
  2. NaCl - strong electrostatic attractive forces between oppositely charged ions need to be broken.
37
Q

What is meant by the term s-block element?

A
  1. Elements with electron arrangement
  2. Differs from previous element
  3. Having 1 more electron in S orbital
38
Q

Compare 1st IE of nitrogen and oxygen.

A
  1. N - 2p electron being lost is unpaired but for O it is paired
  2. 2 electrons in same orbital repel
  3. Easier to remove
  4. IE of N is higher
39
Q

Why does 1st IE increase across a period?

A
  1. Nuclear charge increases
  2. Greater attraction between nucleus and electrons
  3. Electrons pulled towards nucleus decreasing atomic radius
40
Q

Why is 1st IE of aluminium less than Mg?

A
  1. 3p electron more distant from nucleus than 3s
  2. Partially screened by 3s2 electrons
  3. As well as inner electrons
41
Q

Define relative isotopic mass.

A
  1. Mass of an atom of an isotope
  2. Compared with 1/12 of mass of an atom
  3. Of carbon 12
42
Q

Define relative molecular mass.

A
  1. Weighted average mass of a molecule
  2. Of an element or compound
  3. Compared to 1/12 of the mass of an atom
  4. Of carbon 12
43
Q

Describe 2 differences in orbital overlap of sigma and pi bonds.

A
  1. Sigma - single area of overlap and axial overlap

2. Pi - two areas of overlap and parallel overlap

Chemistry (4 decks)

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